CLDAP: Fix domain handling in netlogon requests
    
    1. Stop using getdomainname() as it is often not properly initialized
    2. The code using getdomainname() was not working anyway it was trying to
    look at the function call output in hostname which is always empty at that
    point.
    3. Always check the requested domain matches our own, we cannot reply to
    anything else anyway.
    
    Pre-requisite to fix: https://fedorahosted.org/freeipa/ticket/3639
    
    Signed-off-by: Simo Sorce <simo@redhat.com>