fix(nfsproxy): only increment unmounts counter on successful chroot close

[AdaAibaby]

OnNetworkRelease incremented [nfs.chroot.unmounts] unconditionally, even when [chroot.Close()] returned an error. This meant the difference between [nfs.chroot.mounts] and [nfs.chroot.unmounts] — which is supposed to reflect the number of active mount namespaces — was silently understated whenever a close failed, masking mount namespace leaks in metrics and alerting.

Fix by skipping the counter increment via continue when Close() returns an error. The warning log and map cleanup are unaffected.

A unit test is added to nfs_test.go that injects one successful and one failing Close() call and asserts the counter is incremented exactly once.
/cc @jakubno

[gemini-code-assist]

Code Review

This pull request ensures that the chroot unmounts counter is not incremented if unmounting fails during network release, and introduces a unit test to verify this behavior. There are no review comments or issues to address, and I have no feedback to provide.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: e1e6afcaa6

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".