Use xenial for all py35 jobs

The default nodeset is now bionic which does not include py35, so
we need to explicitly request a nodeset which does.

Change-Id: I8b0ce86299fc1240a14492d9c0823647b41afaa3

.zuul.d/cross-jobs.yaml

@@ -53,6 +53,7 @@
     parent: requirements-cross-test
     description: Run cross-project tests on cinder with py35.
     required-projects: openstack/cinder
+    nodeset: ubuntu-xenial
     vars:
       tox_envlist: py35
 
@@ -69,6 +70,7 @@
     parent: requirements-cross-test
     description: Run cross-project tests on glance with py35.
     required-projects: openstack/glance
+    nodeset: ubuntu-xenial
     vars:
       tox_envlist: py35
 
@@ -85,6 +87,7 @@
     parent: requirements-cross-test
     description: Run cross-project tests on horizon with py35.
     required-projects: openstack/horizon
+    nodeset: ubuntu-xenial
     vars:
       tox_envlist: py35
 
@@ -109,6 +112,7 @@
     parent: requirements-cross-test
     description: Run cross-project tests on keystone with py35.
     required-projects: openstack/keystone
+    nodeset: ubuntu-xenial
     vars:
       tox_envlist: py35
 
@@ -125,6 +129,7 @@
     parent: requirements-cross-test
     description: Run cross-project tests on neutron with py35.
     required-projects: openstack/neutron
+    nodeset: ubuntu-xenial
     vars:
       tox_envlist: py35
 
@@ -149,6 +154,7 @@
     parent: requirements-cross-test
     description: Run cross-project tests on nova with py35.
     required-projects: openstack/nova
+    nodeset: ubuntu-xenial
     vars:
       tox_envlist: py35
 
@@ -165,6 +171,7 @@
     parent: requirements-cross-test
     description: Run cross-project tests on swift with py35.
     required-projects: openstack/swift
+    nodeset: ubuntu-xenial
     vars:
       tox_envlist: py35
 

.zuul.d/jobs.yaml

@@ -31,6 +31,7 @@
 
       Uses tox with the ``py35-check-uc`` environment.
     files: ^upper-constraints.*txt$
+    nodeset: ubuntu-xenial
     vars:
       tox_envlist: py35-check-uc