[v0.22] fix: fix host to virtual service selector syncing

[loft-bot]

Backport from main to v0.22

Original PR Nr.: #2440

Backported Commits:

• 6e32156 fix: fix host to virtual service selector syncing

Original PR Description:

What issue type does this pull request address? (keep at least one, remove the others)
/kind bugfix

This brings the selector syncing inline with the CopyBidirectional logic.

What does this pull request do? Which issues does it resolve? (use resolves #<issue_number> if possible)
resolves #ENG-5654

Please provide a short message that should be published in the vcluster release notes
Fixed an issue where the host service selector should have been synced to the virtual, but it was nullified to match the virtual instead.

What else do we need to know?

Example of what occurred

• Selector was removed from host service
• The change was synced down to the virtual cluster removing it
• The selector was added back to the host service
• The check here was true since the host hadn't changed, and HostLabelsMap returned nil since the vCluster selector was nil.