Remove unneeded Zuul branch matcher

We have implicit branch matchers, so there's no need to add a check for
not-ocata, this job is only run for the branch it's on - like master
now.

Remove it to not confuse Zuul when multiple branches matches and the job
is different.

Also fix heat-container-agent to make linking of /usr/bin/python to python3
conditional on whether it already exists.

Change-Id: I1fec9d19cd14cf2fe2473b7610870e8d669021b9

.zuul.yaml

@@ -177,7 +177,6 @@
     name: magnum-functional-swarm-mode
     parent: magnum-functional-coe
     voting: false
-    branches: ^(?!stable/(newton|ocata)).*$
     vars:
       coe: swarm-mode
     irrelevant-files:
@@ -195,7 +194,6 @@
     name: magnum-functional-dcos
     parent: magnum-functional-coe
     voting: false
-    branches: ^(?!stable/(newton|ocata)).*$
     vars:
       coe: dcos
     irrelevant-files:
@@ -296,7 +294,6 @@
     name: magnum-functional-swarm-mode-multinode
     parent: magnum-functional-multinode-base
     voting: false
-    branches: ^(?!stable/(newton|ocata)).*$
     vars:
       coe: swarm-mode
     irrelevant-files:

dockerfiles/heat-container-agent/Dockerfile

@@ -57,7 +57,7 @@ RUN /tmp/write-os-apply-config-templates.sh
 
 COPY manifest.json service.template config.json.template tmpfiles.template /exports/
 
-RUN ln -s /usr/bin/python3 /usr/bin/python
+RUN if [ ! -f /usr/bin/python ]; then ln -s /usr/bin/python3 /usr/bin/python; fi
 
 COPY launch /usr/bin/start-heat-container-agent