Remove podcidr auto-fill when tkgs routable pod feature is enabled

[chenlin07]

• It's for enabling routable pod feature when creating tkgs cluster

Signed-off-by: Chen Lin linch@vmware.com

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #2060

Describe testing done for PR

Release note

When users want to enable routable pod feature for tkgs, they can set global variable `ENABLE_TKGS_ROUTABLE_POD` to `TRUE`. 
Also, users need to make sure that podcidr is empty when routable pod feature is enabled

PR Checklist

• Squash the commits into one or a small number of logical commits
  
• Use good commit messages
• Ensure PR contains terms all contributors can understand and links all contributors can access

Additional information

Special notes for your reviewer

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220701003943/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[codecov]

Codecov Report

Merging #2806 (6b886bf) into main (a334b86) will decrease coverage by 0.93%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2806      +/-   ##
==========================================
- Coverage   48.52%   47.59%   -0.94%     
==========================================
  Files         446      476      +30     
  Lines       44105    46159    +2054     
==========================================
+ Hits        21404    21970     +566     
- Misses      20658    22096    +1438     
- Partials     2043     2093      +50     

Impacted Files	Coverage Δ
tkg/client/validate.go	61.37% <100.00%> (+0.12%)	⬆️
addons/controllers/machine_controller.go	65.65% <0.00%> (-3.04%)	⬇️
packageclients/pkg/packageclient/package_update.go	83.57% <0.00%> (-1.43%)	⬇️
addons/controllers/clusterbootstrap_controller.go	64.75% <0.00%> (-0.09%)	⬇️
cmd/cli/plugin/cluster/scale.go	17.85% <0.00%> (ø)
cmd/cli/plugin/cluster/set_node_pool.go	14.63% <0.00%> (ø)
...cluster/delete_machinehealthcheck_control_plane.go	16.66% <0.00%> (ø)
...lugin/isolated-cluster/fakes/client_imgpkg_fake.go	32.15% <0.00%> (ø)
...md/cli/plugin/cluster/delete_machinehealthcheck.go	19.23% <0.00%> (ø)
...in/cluster/get_machinehealthcheck_control_plane.go	11.11% <0.00%> (ø)
... and 25 more

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[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220712002823/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220718233940/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220718234534/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[vuil]

Thanks for the changes.
There are some linter errors in the Main CI run that needs fixing, otherwise lgtm.
Please add a note about the testing done.
And definitely add a release note since this has some user-facing implications.

[vuil]

lgtm

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220721003246/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220721003607/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220721010718/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220722122406/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220725083100/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220727152344/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20220728012609/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/2806/20221206021155/clustergen.diff.txt
Author/reviewers:
Please review to verify that the effects on the generated cluster configurations are exactly what the PR intended, and give a thumbs-up if so.