l2switch CSIT tests broken in master

This bug is to track the failures we currently have in CSIT. Basic mininet node pings are not working.

here is one job that sees it:
https://jenkins.opendaylight.org/releng/view/l2switch/job/l2switch-csit-1node-switch-all-beryllium/

as compared to the stable/lithium job that is passing:
https://jenkins.opendaylight.org/releng/view/l2switch/job/l2switch-csit-1node-switch-all-stable-lithium/

it may have been broken for some time, as it was noticed by Luis Gomez back in July:
https://lists.opendaylight.org/pipermail/l2switch-dev/2015-July/000754.html

I don't have a root cause analysis yet, but there are now questions about this
on the mailing lists, so want to make this issue track-able with a bug.