vfs_ceph: call 'ceph_fgetxattr' only if valid fd

vfs_ceph: call 'ceph_fgetxattr' only if valid fd

Align getxattr logic with the rest of xattr hooks: call ceph_fgetxattr
with appropriate io-fd when 'is_pathref' is false; otherwise, call
ceph_getxattr.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15440

Signed-off-by: Shachar Sharon <ssharon@redhat.com>
Reviewed-by: Anoop C S <anoopcs@redhat.com>
Reviewed-by: Guenther Deschner <gd@samba.org>
Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Thu Nov 30 12:32:29 UTC 2023 on atb-devel-224

(cherry picked from commit 83edfcff5ccd8c4c710576b6d5612e0578d168c8)