gfs2: Always update inode ctime in set_acl

Three-entry POSIX ACLs can be stored in the file mode permission bits,
with no need to store them in extended attributes.  When a process sets
such a minimal ACL, the kernel updates the file mode like chmod does,
and removes any existing extended attributes for that ACL.  Make sure
the ctime is always updated in that case.

Fixes xfstest generic/307.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>