Reformat openstack-common.conf

Use the new 'module' option in openstack-common.conf which is a
multi-string option, allowing each module name to be placed on a
separate line.

This makes it much easier to review changes to the modules list.

Change-Id: I2b5c56dbf941b272bd89b0dbe6f651196d90944f
Merge "Reformat openstack-common.conf"