Btrfs: fix transaction handle leak in balance

If we fail to allocate a new data chunk, we were jumping to the error path
without release the transaction handle we got before. Fix this by always
releasing it before doing the jump.

Fixes: 2c9fe83552 ("btrfs: Fix lost-data-profile caused by balance bg")
Signed-off-by: Filipe Manana <fdmanana@suse.com>

fs/btrfs/volumes.c

@@ -3548,12 +3548,11 @@ again:
 
 			ret = btrfs_force_chunk_alloc(trans, chunk_root,
 						      BTRFS_BLOCK_GROUP_DATA);
+			btrfs_end_transaction(trans, chunk_root);
 			if (ret < 0) {
 				mutex_unlock(&fs_info->delete_unused_bgs_mutex);
 				goto error;
 			}
-
-			btrfs_end_transaction(trans, chunk_root);
 			chunk_reserved = 1;
 		}