Check cluster ID during service export

[bansal19]

Issue #, if available: #254

Description of changes:
When exporting a service from Cluster A, we call DiscoverInstances on an entire clusterset in order to determine if there are any changes for the service we wish to export. If there are any changes, all endpoints in that service will be wiped by the endpoints being exported by Cluster A for this service. In order to mitigate this, we must check for the current cluster's endpoints only when calling DiscoverInstances to Cloud Map.

To make sure we obtain the correct endpoints, we will need to invalidate the cache.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #255 (b094033) into main (ba90126) will decrease coverage by 0.27%.
The diff coverage is 94.11%.

@@            Coverage Diff             @@
##             main     #255      +/-   ##
==========================================
- Coverage   70.86%   70.59%   -0.28%     
==========================================
  Files          17       17              
  Lines        1713     1724      +11     
==========================================
+ Hits         1214     1217       +3     
- Misses        417      423       +6     
- Partials       82       84       +2     

Impacted Files	Coverage Δ
...ntrollers/multicluster/serviceexport_controller.go	37.37% <90.90%> (-1.67%)	⬇️
pkg/model/types.go	66.47% <100.00%> (+1.22%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ba90126...b094033. Read the comment docs.

[astaticvoid]

Thanks for the fix and improvements :)