Add functional-py35 gate job

We have functional tests that run under py35, but they are not
currently run in gate. This adds the common job definition to
our locally defined list of tests to run.

Change-Id: Icf477415c7ac54bb007cacc1a1ba905e63fa2780

.zuul.yaml

@@ -7,10 +7,32 @@
         - cinder-tox-bandit-baseline:
             voting: false
         - nova-multiattach
+        - openstack-tox-functional-py35:
+            branches: ^(?!driverfixes/).*$
+            irrelevant-files:
+              - ^.*\.rst$
+              - ^api-ref/.*$
+              - ^cinder/hacking/.*$
+              - ^cinder/locale/.*$
+              - ^cinder/tests/unit.*$
+              - ^contrib/block-box.*$
+              - ^doc/.*$
+              - ^releasenotes/.*$
     gate:
       jobs:
         - cinder-tox-compliance
         - nova-multiattach
+        - openstack-tox-functional-py35:
+            branches: ^(?!driverfixes/).*$
+            irrelevant-files:
+              - ^.*\.rst$
+              - ^api-ref/.*$
+              - ^cinder/hacking/.*$
+              - ^cinder/locale/.*$
+              - ^cinder/tests/unit.*$
+              - ^contrib/block-box.*$
+              - ^doc/.*$
+              - ^releasenotes/.*$
 
 - job:
     # Previously named legacy-tempest-dsvm-full-lio