[Virtio-fs] [virtiofsd-rs] MR opened: Fix xattr for non-regular, non-directory files

[virtiofs-bot at sinrega.org]

We can only use f{set,get,remove,list}xattr functions on regular and
directory files. For other types of files, use fchdir and the ...xattr
version of the syscall, instead of the f...xattr alternative.

This is a port of virtiofsd commit bdfd6678834 (virtiofsd: Fix xattr
operations) by Misono Tomohiro.

Signed-off-by: Sergio Lopez <slp at redhat.com>
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https://gitlab.com/virtio-fs/virtiofsd-rs/-/merge_requests/32