Make python3 rally job voting in Neutron

This makes the python3 rally job voting in Neutron and alters
the python2 job to only run on the stable branches.

Note that this job is not in the gate queue even though it is
voting. This is the way the current rally job that it is replacing
is configured.

Change-Id: Ib478da40a5df8f4060f61d251570957fbc363a6a

jenkins/jobs/projects.yaml

@@ -7513,7 +7513,7 @@
           telemetry: '0'
       - gate-rally-dsvm-py35-neutron-{name}-{node}{suffix}:
           node: ubuntu-xenial
-          suffix: '-nv'
+          suffix: ''
           telemetry: '0'
       - '{pipeline}-grenade-dsvm-neutron-multinode-{node-release}{suffix}':
           pipeline: gate

zuul/layout.yaml

@@ -1994,6 +1994,10 @@ jobs:
   - name: ^gate-tempest-dsvm-neutron-pg-full-ubuntu-(trusty|xenial)
     voting: false
 
+  # non py35 rally xenial job should only run on newton. master is py35
+  - name: ^gate-rally-dsvm-neutron-neutron-ubuntu-xenial
+    branch: ^stable/newton
+
   # scenario tests for neutron-dynamic-routing can be run on ocata and later
   - name: ^gate-neutron-dynamic-routing-dsvm-tempest-scenario.*$
     branch: ^(?!stable/newton).*$
@@ -12251,7 +12255,7 @@ projects:
       - gate-neutron-dsvm-fullstack-ubuntu-xenial
       - gate-rally-dsvm-neutron-neutron-ubuntu-trusty
       - gate-rally-dsvm-neutron-neutron-ubuntu-xenial
-      - gate-rally-dsvm-py35-neutron-neutron-ubuntu-xenial-nv
+      - gate-rally-dsvm-py35-neutron-neutron-ubuntu-xenial
       - gate-tempest-dsvm-neutron-dvr-ubuntu-trusty
       - gate-tempest-dsvm-neutron-dvr-ubuntu-xenial
       - gate-tempest-dsvm-neutron-identity-v3-only-full-ubuntu-xenial-nv