bcachefs: fix restart handling in bch2_rename2()

This should be impossible to hit in practice; the first lookup within a
transaction won't return a restart due to lock ordering, but we're
adding fault injection for transaction restarts and shaking out bugs.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Author: Kent Overstreet

fs/bcachefs/fs.c

@@ -871,7 +871,7 @@ static int bch2_rename2(struct mnt_idmap *idmap,
 	ret   = bch2_subvol_is_ro_trans(trans, src_dir->ei_inum.subvol) ?:
 		bch2_subvol_is_ro_trans(trans, dst_dir->ei_inum.subvol);
 	if (ret)
-		goto err;
+		goto err_tx_restart;
 
 	if (inode_attr_changing(dst_dir, src_inode, Inode_opt_project)) {
 		ret = bch2_fs_quota_transfer(c, src_inode,