DAOS-16932 dfuse: do not flush dentries at fs stop

[jxiong]

This operation will never succeed since the file system is already unmounted. Therefore it always returns EBADF from libfuse.

Actually, it should not attempt to do that since dentries will be cleared by kernel at the time of unmounting.

Change-Id: I18eaffc0437d05e5ccc50d0a548451c4837cb1f9
Signed-off-by: Jinshan Xiong [email protected]
Run-GHA: true

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[github-actions]

Ticket title is 'dfuse should not try to invalidate dentries at fs stop'
Status is 'Open'
https://daosio.atlassian.net/browse/DAOS-16932

[jolivier23]

Add * (C) Copyright 2025 Google LLC after Intel lines. New githook will do this for you

[jolivier23]

I think if you do an amend commit, it will do it if you have githook installed