After getting confirmation from Guenther, add 3 changes we'll

After getting confirmation from Guenther, add 3 changes we'll
ultimately need to fix bug #6099 Samba returns incurrate capabilities list.
1). Add a comment to point out that r->in.negotiate_flags is an aliased pointer to
r->out.negotiate_flags.
2). Ensure we return NETLOGON_NEG_STRONG_KEYS in our flags
return if the client requested it.
3). Clean up the error exits so we always return the same
way.
Signed off by Guenther.
Jeremy.