Btrfs: fix possible memory leak in replace_path()

In replace_path(), if read_tree_block() fails, we cannot return
directly, we should free some allocated memory otherwise memory
leak happens.

Similar to Wang's "Btrfs: fix possible memory leak in the
find_parent_nodes()" patch, the current commit fixes an issue that
is related to the "Btrfs: fix all callers of read_tree_block"
commit.
Signed-off-by: NStefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: NJosef Bacik <jbacik@fusionio.com>

fs/btrfs/relocation.c

@@ -1773,7 +1773,7 @@ int replace_path(struct btrfs_trans_handle *trans,
 			if (!eb || !extent_buffer_uptodate(eb)) {
 				ret = (!eb) ? -ENOMEM : -EIO;
 				free_extent_buffer(eb);
-				return ret;
+				break;
 			}
 			btrfs_tree_lock(eb);
 			if (cow) {