Install oslo.service via pip

python-oslo-service is not yet packaged for Delorean, causing
multiple services that have switched to this library to break.
To resolve that problem, we have a short term fix of installing
the oslo.service via pip in the base image.

Change-Id: Iff3410ec90b25b239ee49cc725ef224fa80e7aee
Closes-Bug: #1469821