Kickstart UI: Remove trailing comma when converting a string map to string

[miclettej]

Fixes issue with conversion of string map leaving trailing comma on converted single string

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #

Describe testing done for PR

Confirmed that config yaml is written without unexpected trialing comma in converted maps

Release note

Fixes bug in UI related to AVI Labels causing cluster creation failure

Additional information

Special notes for your reviewer

[github-actions]

Cluster Generation A/B Results:
https://storage.googleapis.com/tkg-clustergen/3615/20221011031719/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/3615/20221011033754/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/3615/20221011043744/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 #3615 (60bf18c) into main (7efdbec) will decrease coverage by 0.86%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3615      +/-   ##
==========================================
- Coverage   46.27%   45.40%   -0.87%     
==========================================
  Files         400      425      +25     
  Lines       39573    41139    +1566     
==========================================
+ Hits        18311    18679     +368     
- Misses      19572    20755    +1183     
- Partials     1690     1705      +15     

Impacted Files	Coverage Δ
tkg/tkgconfigproviders/helper.go	100.00% <100.00%> (ø)
cmd/cli/plugin/cluster/create.go	41.30% <0.00%> (ø)
cmd/cli/plugin/cluster/available_upgrade.go	16.32% <0.00%> (ø)
.../cli/plugin/cluster/get_machinehealthcheck_node.go	9.30% <0.00%> (ø)
cmd/cli/plugin/cluster/osimage.go	100.00% <0.00%> (ø)
cmd/cli/plugin/cluster/kubeconfig_get.go	8.82% <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)
cmd/cli/plugin/cluster/set_node_pool.go	14.63% <0.00%> (ø)
... and 19 more

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[swalner-vmware]

LGTM

[danniel1205]

lgtm, thanks for the PR