Add 'ovn-controller' service

Add 'ovn-controller' service

Presently the ovn-controller service (puppet/services/neutron-compute-plugin-ovn.yaml)
is started only on compute nodes. But for the cases where the controller nodes
provide the north/south traffic, we need ovn-controller service runninng in controller
nodes as well.

This patch
 - Renames the neutron-compute-plugin-ovn.yaml to ovn-controller.yaml which makes more
   sense and sets the service name as 'ovn-controller'.
 - Adds the service 'ovn-controller' to Controller and Compute roles.
 - Adds the missing 'upgrade_tasks' section in ovn-dbs.yaml and ovn-controller.yaml

Depends-On: Ie3f09dc70a582f3d14de093043e232820f837bc3
Depends-On: Ide11569d81f5f28bafccc168b624be505174fc53
Change-Id: Ib7747406213d18fd65b86820c1f86ee7c39f7cf5