In the tests which are using tcpdump to check if traffic is going
through the right node(s) there was only check if something was captured
or not. But in case of failure we didn't know what was captured what
caused issue.
Now this patch adds logging of the packets captured on all of the nodes
in case if the assertion in test failed. Hopefully that will help
debugging issues like in the related bug.
Related-bug: #OSPRH-11312
Change-Id: I1025ae0c9dbb50d187b2827a8a7c4de864e35875
81d9dc6831