Use host keytab to connect to remote server on DL0
    
    Since host enrollment was implemented in DL0, use
    the host keytab to connect to remote api and perform
    certain actions to merge DL1 and DL0 replica install
    workflows.
    
    https://fedorahosted.org/freeipa/ticket/6392
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>