Convert to a more modern form of openstack-common.conf

One module per line is the new hotness. I've also sorted the
modules alphabetically. There are no changes to your imports, but
this makes it easier for oslo maintainers to keep your imports up
to date.

Change-Id: I7581f4ad2ed853742a98aa6d6d4e9e0aeebce8fa
Merge "Convert to a more modern form of openstack-common.conf"