Fix issue where API gateways were being mis-labeled as Sidecar proxies

[t-eckert]

Changes proposed in this PR:

• Fix an issue where pods running API Gateway were being mis-labeled as "Sidecar" pods

How I've tested this PR:

• Edited the unit test to test the correct behavior.
• Manual testing against a cluster

How I expect reviewers to test this PR:

• Running the unit tests

Checklist:

• [x] Tests added
• [ ] CHANGELOG entry added

  HashiCorp engineers only, community PRs should not add a changelog entry. Entries should use present tense (e.g. Add support for...)

[t-eckert]

I don't feel that this needs a CHANGELOG entry unless Envoy debugging goes out before this gets merged. The bug never reached production otherwise.

[thisisnotashwin]

Can we investigate why the acceptance tests are failing before we merge this?

[t-eckert]

Can we investigate why the acceptance tests are failing before we merge this?

Oh yeah, that's been most of my day so far. It's weird.