Remove Python packaging files

Remove Python packaging files

Since we don't release releng as a python project, it doesn't make much
sense to include a setup.py.

The jjb testenv in tox.ini is modified to pin jenkins-job-builder and no
longer require setup.py nor jjb/test-requirements.txt, and the modules
testenv is moved to it's own tox.ini under modules.

Locally testing of jjb can still be done using:

  tox -e jjb

Change-Id: I512b1a8f9cd7d48a2f14b1bbe966b525793a6fe3
Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>