btrfs: remove unnecessary cur_trans set before goto loop in join_transaction

In the big loop, cur_trans will be set fs_info->running_transaction
before it's used. And after kmem_cache_free it and goto loop, it will
be setup again. No need to setup it immediately after freed.
Signed-off-by: NWang Sheng-Hui <shhuiw@gmail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

fs/btrfs/transaction.c

@@ -111,7 +111,6 @@ static noinline int join_transaction(struct btrfs_root *root, int type)
 		 * to redo the trans_no_join checks above
 		 */
 		kmem_cache_free(btrfs_transaction_cachep, cur_trans);
-		cur_trans = fs_info->running_transaction;
 		goto loop;
 	} else if (fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR) {
 		spin_unlock(&fs_info->trans_lock);