Migrate patrol jobs to bionic(Ubuntu LTS 18.04)

This commit switch the patrole gate testing on Bionic (Ubuntu LTS 18.04)
from stein onwards.

patrole use base jobs from Tempest so we do not need to override the
nodeset. All magic happen with Tempest/Devstack base jobs (Depends-On patch).

Stable branch testing jobs like patrole-member-rocky on xenial for
backwards compatibility.

Depends-On: https://review.openstack.org/#/c/618169/

Change-Id: I7e3ec9079da98e111aa750004a284a0257cb86ce
diff --git a/.zuul.yaml b/.zuul.yaml
index b2b59a2..161f8aa 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -87,16 +87,19 @@
 
 - job:
     name: patrole-member-rocky
+    nodeset: openstack-single-node-xenial
     parent: patrole-member
     override-checkout: stable/rocky
 
 - job:
     name: patrole-member-queens
+    nodeset: openstack-single-node-xenial
     parent: patrole-member
     override-checkout: stable/queens
 
 - job:
     name: patrole-member-pike
+    nodeset: openstack-single-node-xenial
     parent: patrole-member
     override-checkout: stable/pike