Make BGP prefix checking less flaky

[wenovus]

Currently it's failing because the Await check before the Get wait for any prefix rather than the prefix Get is looking for. This makes some of the checks fail intermittently when multiple prefixes are checked at the same time.

[github-actions]

Pull Request Test Coverage Report for Build 9407860534

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 224 unchanged lines in 5 files lost coverage.
• Overall coverage increased (+0.01%) to 2.802%

---

Files with Coverage Reduction	New Missed Lines	%
sysrib/zapi.go	9	71.5%
gnsi/pathz/pathz.go	13	84.03%
dataplane/saiserver/saiserver.go	29	61.86%
dataplane/saiserver/ports.go	84	82.77%
dataplane/saiserver/switch.go	89	86.33%

Totals
Change from base Build 9321685208:	0.01%
Covered Lines:	18441
Relevant Lines:	658042

---

💛 - Coveralls

[DanG100]

this test is still failing on the presubmit

[wenovus]

this test is still failing on the presubmit

Yeah I'm not sure what's going on, the test consistently passes locally. Will dig through the logs.