winbindd: let WBFLAG_PAM_GET_PWD_POLICY only fake the password policy

winbindd: let WBFLAG_PAM_GET_PWD_POLICY only fake the password policy

As WBFLAG_PAM_GET_PWD_POLICY is only kept for legacy external callers
of libwbclient, we should avoid having the complexity to do additional
network roundtrips to our domain, while we still can't garantee that
the returned password policy actually represents the reality for
the current authentication.

Instead we're calculating r->data.auth.policy.expire and
r->data.auth.policy.min_passwordage based on the effective
{last,allow,force}_password_change values.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Christof Schmitt <cs@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Thu Apr  6 14:03:09 CEST 2017 on sn-devel-144