Dont run puppet 4 unit on master

Was deprecated in Stein so we continue to run them
there but for Train it's not supported so removing
testing on master.

Change-Id: I062c7e21fa8a2aa35fbf8768c752715868da5132

zuul.d/libraries.yaml

@@ -5,6 +5,7 @@
     name: puppet-openstack-libraries-puppet-unit-4.8-centos-7
     parent: puppet-openstack-libraries-puppet-unit-base
     nodeset: centos-7
+    branches: ^stable/(ocata|pike|queens|rocky|stein)$
     vars:
       puppet_gem_version: 4.8
 

zuul.d/linters.yaml

@@ -12,6 +12,7 @@
 - job:
     name: puppet-openstack-syntax-4-ubuntu-bionic
     parent: puppet-openstack-syntax-base
+    branches: ^stable/(ocata|pike|queens|rocky|stein)$
     vars:
       puppet: 4
 
@@ -55,6 +56,7 @@
     name: puppet-openstack-libraries-puppet-syntax-4-centos-7
     parent: puppet-openstack-libraries-puppet-syntax
     nodeset: centos-7
+    branches: ^stable/(ocata|pike|queens|rocky|stein)$
     vars:
       puppet: 4
 

zuul.d/unit.yaml

@@ -5,6 +5,7 @@
     name: puppet-openstack-unit-4.8-centos-7
     parent: puppet-openstack-unit-base
     nodeset: centos-7
+    branches: ^stable/(ocata|pike|queens|rocky|stein)$
     vars:
       puppet_gem_version: 4.8