Btrfs, fix memory leaks in error paths

Stanse found 2 memory leaks in relocate_block_group and
__btrfs_map_block. cluster and multi are not freed/assigned on all
paths. Fix that.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: linux-btrfs@vger.kernel.org
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index a972868..ed3e4a2 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3281,8 +3281,10 @@
 		return -ENOMEM;
 
 	path = btrfs_alloc_path();
-	if (!path)
+	if (!path) {
+		kfree(cluster);
 		return -ENOMEM;
+	}
 
 	rc->extents_found = 0;
 	rc->extents_skipped = 0;