NetworkPolicy e2e test should wait for Pod ready

[tnqn]

What type of PR is this?
/kind flake

What this PR does / why we need it:
The test "should enforce egress policy allowing traffic to a server in a
different namespace based on PodSelector and NamespaceSelector
[Feature:NetworkPolicy]" is flaky because it doesn't wait for the server
Pod to be ready before testing traffic via its service, then even the
NetworkPolicy allows it, the SYN packets will be rejected by iptables
because the service has no endpoints at that moment.

This PR fixes it by making it wait for Pods to be ready like other
tests.

Which issue(s) this PR fixes:

Fixes #88340

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

Hi @tnqn. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[tnqn]

cc: @lzang (not able to add you to reviewers)

[johnbelamaric]

/ok-to-test
/priority important-soon

[johnbelamaric]

/assign

[johnbelamaric]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johnbelamaric, tnqn

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• test/e2e/network/OWNERS [johnbelamaric]

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