Rename our base job
Rename our base job

Rename to add "-base" to the base job to follow Zuul conventions, also
add abstract to mark that this cannot run on its own and needs to be
inherited from.

Change-Id: Ic2228244e787395be1c5dc77a92e2ff352d47106

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals