Generate testr_results.html for neutron functional job

Tweak job post_test_hook script to generate testr results
the same way other jobs do, with a pretty html view that
is easy to digest and navigate.

Closes-bug: #1401340

Change-Id: Ib355f34917580b88bda3d550e33fc630a8e7120b
Merge "Generate testr_results.html for neutron functional job"