ipa commands: print 'IPA is not configured' when ipa is not setup
Some commands print tracebacks or unclear error message when
they are called on a machine where ipa packages are installed but
IPA is not configured.
Consistently report 'IPA is not configured on this system' in this
case.
Related to https://pagure.io/freeipa/issue/6261
Reviewed-By: Christian Heimes <cheimes@redhat.com>