Let Nova jobs vote again

After the jobs where modified to run only Nova test cases
we can restore Nova job in the gate pipeline.

Change-Id: Idb136afc91d177a3d091e45c8130f79609b6f41e

zuul.d/devstack-tobiko-nova.yaml

@@ -7,6 +7,9 @@
     check:
       jobs:
         - devstack-tobiko-nova
+    gate:
+      jobs:
+        - devstack-tobiko-nova
     periodic:
       jobs:
         - devstack-tobiko-nova
@@ -21,9 +24,18 @@
     parent: devstack-tobiko-minimal
     required-projects:
       - openstack/nova
-    voting: false
+    voting: true
     vars:
       test_workflow: create-resources-nova
+    irrelevant-files: &FAULTS_IRRELEVANT_FILES
+      - ^.*\.rst$
+      - ^doc/
+      - ^infrared_plugin/
+      - ^releasenotes/
+      - ^report/
+      - ^tobiko/tests/functional/
+      - ^tobiko/tests/scenario/
+      - ^tobiko/tests/unit/
 
 - job:
     name: devstack-tobiko-nova-centos