Zuul: add checks for fedora

This PS adds fedora to the list of distros that OSH-Infra is checked
against.

It also makes the CentOS gate non-voting untill stability issues are
resolved.

Change-Id: I321ee592eeca75f66090747a74a02c7c0ba80bc5

.zuul.yaml

@@ -16,8 +16,12 @@
     name: openstack/openstack-helm-infra
     check:
       jobs:
-        - openstack-helm-infra-ubuntu
-        - openstack-helm-infra-centos
+        - openstack-helm-infra-ubuntu:
+            voting: true
+        - openstack-helm-infra-centos:
+            voting: false
+        - openstack-helm-infra-fedora:
+            voting: false
     gate:
       jobs:
         - openstack-helm-infra-ubuntu
@@ -57,6 +61,24 @@
         nodes:
           - node-1
           - node-2
+
+- nodeset:
+    name: openstack-helm-fedora
+    nodes:
+      - name: primary
+        label: fedora-26
+      - name: node-1
+        label: fedora-26
+      - name: node-2
+        label: fedora-26
+    groups:
+      - name: primary
+        nodes:
+          - primary
+      - name: nodes
+        nodes:
+          - node-1
+          - node-2
 - job:
     name: openstack-helm-infra-ubuntu
     pre-run: tools/gate/playbooks/zuul-pre
@@ -68,3 +90,9 @@
     pre-run: tools/gate/playbooks/zuul-pre
     run: tools/gate/playbooks/zuul-run
     nodeset: openstack-helm-centos
+
+- job:
+    name: openstack-helm-infra-fedora
+    pre-run: tools/gate/playbooks/zuul-pre
+    run: tools/gate/playbooks/zuul-run
+    nodeset: openstack-helm-fedora