fs: dlm: add missing spin_unlock

This patch fixes commit dc52cd2e ("fs: dlm: fix F_CANCELLK to cancel
pending request") that we don't unlock the ops_lock in a rate case when
a waiter cannot be found. This case can only happen when cancellation of
plock operation was successful but no kernel waiter was being found.

Fixes: dc52cd2e ("fs: dlm: fix F_CANCELLK to cancel pending request")
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/plock.c

@@ -398,6 +398,7 @@ int dlm_posix_cancel(dlm_lockspace_t *lockspace, u64 number, struct file *file,
 		 */
 		op = plock_lookup_waiter(&info);
 		if (WARN_ON_ONCE(!op)) {
+			spin_unlock(&ops_lock);
 			rv = -ENOLCK;
 			break;
 		}