Explicitly set jobs to ML2/OVS

Devstack is changing the Neutron default to OVN backend. This patch
is asserts that neutron-tempest-plugin gate will not get broken by
that change by explicitly configuring stable jobs to continue to run
with ML2/OVS.

Change-Id: Ibc1594d0296b31af82776eea84b1d3dea5a4dac7
Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>
7 files changed