Add generic tox job (multiple playbooks)

Here we now support 3 tox jobs; cover, linters and py27.

As you can see by looking at the code, we are not defining any
variables (vars) in .zuul.yaml. This means, we create 3 separate
playbooks (tox-cover.yaml, tox-py27, tox-linters.yaml) which then
contain the variables we need for our tox role.

Change-Id: I42f8855f44da51cb3d23f1825bd3258937543b2f
Signed-off-by: Paul Belanger <pabelanger@redhat.com>
13 files changed