cifs: Fix xid leak in cifs_get_file_info_unix()

If stardup the symlink target failed, should free the xid,
otherwise the xid will be leaked.

Fixes: 76894f3e

 ("cifs: improve symlink handling for smb2+")
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>