Ifgrp different from a0a not suppported

The check has hardcoded a0a/a0b. However we are using a different naming convention.
Therefore we did not get any warnings when a port went down.
It would be nice to have it first check for the ifgrp interfaces in the cluster. Iterate across that list for the member ports.
Now we have fixed it by hardcoding our own ifgrp interface names but that is not really elegant/portable.
