[COOK-3736] - add omnios support

* omnios platform to .kitchen.yml (uses upstream box from OmniTI)
* Notes about omnios in TESTING.md
* omnios service name is `system/rsyslogd`, use the same modules, and group as smartos
* the SMF manifest for rsyslogd by default using the omniti package of
  rsyslog points to /opt/omni's etc location, so write a custom manifest
  and import it