ipalib.constants: Remove default domain, realm, basedn, xmlrpc_uri, ldap_uri
    
    Domain, realm, basedn, xmlrpc_uri, ldap_uri do not have any reasonable default.
    This patch removes hardcoded default so the so the code which depends
    on these values blows up early and does not do crazy stuff
    with default values instead of real ones.
    
    This should help to uncover issues caused by improper ipalib
    initialization.
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>