Update oslo-config-generation code

Oslo's config generator has been moved under oslo.config, which doesn't
require using a bash script anymore.

The patch removes the old scripts and updates the generation task in
tox.ini

Closes-bug: #1373800

Change-Id: Ia757b0d141f8557144108d386496d1e9bfc7333f
Merge "Update oslo-config-generation code"