KRA install: show installation message only if install really started
    
    Message that installation started/failed was shown even when
    install_check fail (installation itself did not start).
    This commit show messages only if installation started.
    
    Enhacement for https://fedorahosted.org/freeipa/ticket/5455
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>