fs/ntfs3: Move ni_lock_dir and ni_unlock into ntfs_create_inode

Now ntfs3 locks mutex for smaller time.
Theoretically in successful cases those locks aren't needed at all.
But proving the same for error cases is difficult.
So instead of removing them we just move them.

Reviewed-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>