Update vs backup service tests with retries

[shaun-nx]

Proposed changes

Updates test_virtual_server_backup_service tests with retries when asserting that the backup services is in the upstream

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4a9832a) 52.03% compared to head (31609af) 52.03%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4797   +/-   ##
=======================================
  Coverage   52.03%   52.03%           
=======================================
  Files          60       60           
  Lines       17313    17313           
=======================================
  Hits         9009     9009           
  Misses       7993     7993           
  Partials      311      311           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.