CI test VFlowInterRouterTest fails to clean up the test routers

[kgiusti]

After running the test I still have routers running in the background:

ps -f -C skrouterd
UID          PID    PPID  C STIME TTY          TIME CMD
kgiusti  1758069    2860  0 10:04 pts/0    00:00:03 skrouterd -c INTB.conf -T -I /home/kgiusti/work/skupper/skupper-router/python
kgiusti  1758070    2860  0 10:04 pts/0    00:00:02 skrouterd -c EdgeB.conf -T -I /home/kgiusti/work/skupper/skupper-router/python

I suspect the overridden teardown class method needs to invoke the super as well.