Use WSGI worker process configuration in Apache templates inline
with other OpenStack Charms.
Additionally:
* fixes typos in functional tests;
* removes zesty-ocata (zesty is EoL);
* fixes tox.ini to run xenial-ocata as Panko is only available in Ocata;
* fixes src/test-requirements.txt to use a github url instead of lp;
* adds a repo link now that Panko is in OpenStack repos.
Change-Id: If24ad0ee3e7cc7282186e8a80c8c2174ab4daa02
Closes-Bug: 1748432
Dmitrii Shcherbakov