test: fix race condition

[ipochi]

Fixes the race condition when running the test

client_test.go:134: client.endpointConn not released
E0330 19:34:12.841766   16710 client.go:489] "could not send DIAL_RSP" err="expected send error" dialID=111 connectionID=1 dialAddress="127.0.0.1:57901"
E0330 19:34:12.842510   16710 client.go:440] "close response failure" err="expected send error" ="(MISSING)"
E0330 19:34:16.834985   16710 client.go:388] "could not read stream" err="timeout recv" serverID="" agentID=""
E0330 19:34:16.838832   16710 client.go:388] "could not read stream" err="timeout recv" serverID="" agentID=""
E0330 19:34:16.839057   16710 client.go:388] "could not read stream" err="timeout recv" serverID="" agentID=""
E0330 19:34:17.842124   16710 client.go:388] "could not read stream" err="timeout recv" serverID="" agentID=""
FAIL
FAIL	sigs.k8s.io/apiserver-network-proxy/pkg/agent	8.111s
?   	sigs.k8s.io/apiserver-network-proxy/pkg/agent/metrics	[no test files]
FAIL

[k8s-ci-robot]

Hi @ipochi. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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.

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[cheftako]

/ok-to-test

[cheftako]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cheftako, ipochi

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