[3.0] Revert "smb2: fix anonymous login"

This reverts commit 205963ad.

According to git blame on libsmb2, anonymous login was always enabled with a NULL password.

I don't know what happened when I tested this reverted commit, I may have mix up VLC or/and smb/smb2/dsm builds.

For future reference, see libsmb2/lib/ntlmssp.c:

...
encode_ntlm_auth(...)
{
...
    if (auth_data->password == NULL) {
            anonymous = 1;
            goto encode;
    }
...
}

Fixes #27113 (closed)