s4:rpc_server: Do some checks of LogonSamLogon flags

s4:rpc_server: Do some checks of LogonSamLogon flags

This matches a Windows Server, at least if it is itself a
DC of the forest root and the requested domain is the local domain of the DC.
Both constraints are true on a Samba AD DC, as we don't really support
trusts yet.

Pair-Programmed-With: Andreas Schneider <asn@samba.org>

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Andreas Schneider <asn@samba.org>
Autobuild-User(master): Andreas Schneider <asn@cryptomilk.org>
Autobuild-Date(master): Fri Jun  9 17:06:04 CEST 2017 on sn-devel-144