v2/internal/proxy: TestClientInitialization failed

[flaky-bot]

Note: #1837 was also for this test, but it was closed more than 10 days ago. So, I didn't mark it flaky.

---

commit: c5f4677
buildURL: https://github.com/GoogleCloudPlatform/cloud-sql-proxy/actions/runs/8495069303
status: failed

[flaky-bot]

Looks like this issue is flaky. 😟

I'm going to leave this open and stop commenting.

A human should fix and close this.

---

When run at the same commit (c5f4677), this test passed in one build (https://github.com/GoogleCloudPlatform/cloud-sql-proxy/actions/runs/8495069303) and failed in another build (https://github.com/GoogleCloudPlatform/cloud-sql-proxy/actions/runs/8495069303).

[enocom]

=== RUN TestClientInitialization/with_TCP_port_for_non_functional_instance
2024/03/31 02:14:11 [proj:region:fakeserver] could not listen to address :50000: listen tcp :50000: bind: address already in use
proxy_test.go:329: want error = nil, got = [proj:region:fakeserver] Unable to mount socket: listen tcp :50000: bind: address already in use
--- FAIL: TestClientInitialization (0.01s)