Fix ipa hbactest output
    
    ipa hbactest command produces a Traceback (TypeError: cannot concatenate
    'str' and 'bool' objects)
    This happens because hbactest overrides output_for_cli but does not
    properly handle the output for 'value' field. 'value' contains a boolean
    but it should not be displayed (refer to ipalib/frontend.py,
    Command.output_for_cli()).
    
    Note that the issue did not appear before because the 'value' field
    had a flag no_display.
    
    https://fedorahosted.org/freeipa/ticket/6157
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>