dm thin: fix missing pool reference count decrement in pool_ctr error path

commit ba30670f4d5292c4e7f7980bbd5071f7c4794cdd upstream.

Fixes: ac8c3f3df ("dm thin: generate event when metadata threshold passed")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index e22e6c8..7073b22 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2959,7 +2959,7 @@
 						metadata_low_callback,
 						pool);
 	if (r)
-		goto out_free_pt;
+		goto out_flags_changed;
 
 	pt->callbacks.congested_fn = pool_is_congested;
 	dm_table_add_target_callbacks(ti->table, &pt->callbacks);