Doc: Use VersionInfo from pbr and remove openstack common modules

The setup was migrated to pbr in d2ff8c0, but the documentation
build is still using VersionInfo from a bundled version of the
openstack common modules.

Migrate the documentation build to use VersionInfo from pbr, and
remove the no-longer-used common modules.

Change-Id: I7dcd5b0328613c7c72efa2df8c26d9c9b1d47c0f
Merge "Doc: Use VersionInfo from pbr and remove openstack common modules"