check for installed dependencies when *not* in standalone mode
    
    The condition that controls when to check for samba dependencies was
    misformulated. The check should be run when the installer is *not* run
    as standalone. In standalone mode the check is already made in different
    place so the original code triggered it twice.
    
    https://fedorahosted.org/freeipa/ticket/6630
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>