[3.5] fix(defrag): close temp file in case of error

[ghouscht]

See #18841 for details. Backport of #18851 to 3.5

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

[k8s-ci-robot]

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[ghouscht]

/assign @ahrtr

Should I prepare a changelog entry as well?

[ahrtr]

/ok-to-test

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahrtr, ghouscht

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[ahrtr]

PLease also update the changelog for both. 3.5 and 3.4, thx

[mmorel-35]

This will make go vet fail and is already causing trouble on main https://prow.k8s.io/view/gs/kubernetes-ci-logs/pr-logs/pull/etcd-io_etcd/18821/pull-etcd-verify/1854634839446130688#1:build-log.txt%3A838