nfsd: use ATTR_CTIME_SET for delegated ctime updates

nfsd: use ATTR_CTIME_SET for delegated ctime updates

Ensure that notify_change() doesn't clobber a delegated ctime update
with current_time() by setting ATTR_CTIME_SET for those updates.

Don't bother setting the timestamps in cb_getattr_update_times() in the
non-delegated case. notify_change() will do that itself.

Fixes: 7e13f4f8d27d ("nfsd: handle delegated timestamps in SETATTR")
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>