Add testcases for IcingaDB inventory #280
Description
We already have testing for the inventory plugin that can be copied for icingadb, but I believe we need to update our test docker container to support icingadb. And this might get a bit cumbersome.
The test image resides in https://github.com/telekom-mms/icinga2-docker/
Originally posted by @schurzi in #274 (comment)