[3.4] Avoid deadlock in etcd.Close when stopping during bootstrapping

[joshuazh-x]

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

#19150: Backport #19139 to 3.4

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @joshuazh-x. Thanks for your PR.

I'm waiting for a etcd-io 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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[ivanvc]

/retitle [3.4] Avoid deadlock in etcd.Close when stopping during bootstrapping
/ok-to-test

[ahrtr]

Suggested change

	"github.com/stretchr/testify/require"
	"github.com/stretchr/testify/require"