Remove a check on p->vuid in _netr_LogonSamLogon/off

Remove a check on p->vuid in _netr_LogonSamLogon/off

This is in preparation of removing p->vuid completely. I don't think this check
here makes any sort of sense, it only proves that the user having done the
session setup on its way to the schannel bind (ususally anonymous) did not do a
logoff in between. But this would have been caught way before this in
reply_pipe_write_and_X.
(This used to be commit fbc00460f8deaa57bfbf16b12d29acec56578b63)