Readd openstack-tox-py35-with-neutron-lib-master
Readd openstack-tox-py35-with-neutron-lib-master

Job openstack-tox-py35-with-neutron-lib-master is a master only job and
should have stayed in project-config for networking-midonet like it was
done for other repos. Readd it again.

Change-Id: Ib7aa97464bf53339bd10dc7f7a88d8abea33598c

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