This patch update browser from Chrome to Firefox
in karma.conf.js because nodejs fails with Chrome
browser as not able to access some URL.
So let's switch to Firefox browser now then we can
use Chrome browser in future once this issue is resolved.
It also updates few packages in 'lower-constraints.txt'
to fix lower-constraints job.
Change-Id: I1467fd00f3746c5c84233f31c8d41609d0345303