Make gate-manila-python34 votable
Make gate-manila-python34 votable

Manila project has passing tox job gate-manila-python34.
Make it voting, add to 'gate' queue and, also, exclude it from
stable branches for Juno and Kilo releases, because it is expected
to fail there.

Change-Id: I1a3ec299a0b3b405775463087780e53d35e6249e

openstack-infra/project-config,openstack-infra/project-config,dongwenjuan/project-config,dongwenjuan/project-config,Tesora/tesora-project-config,noorul/os-project-config,Tesora/tesora-project-config,noorul/os-project-config