Update networking-ovn Neutron API tests job
Update networking-ovn Neutron API tests job

This patch is modifying the neutron-api job for networking-ovn to make
it use the devstack configuration from the networking-ovn tree.

Now, subsequent patches to tweak the test REGEX (or other
configurations) can be sent to the networking-ovn project directly
instead of project-config.

Change-Id: I0f422a2ae2e1a4a56fc23b1afd4766fa2a503968
Depends-On: Idee833a90c2c2dacea8c92ff58f67f6c3822bb9e

openstack-infra/project-config,openstack-infra/project-config