Pin stable branch jobs (victoria to zed) nodeset to Ubuntu Focal (20.04)

In 2023.1 cycle. we are moving the default distro
version of Ubuntu to Jammy (22.04)[1] so we need to pin
the nodeset for stable branch job in master gate so that
they continue run on their supporting distro version which is
Ubuntu Focal from stable/victoria until stable/zed.

[1] https://governance.openstack.org/tc/goals/selected/migrate-ci-jobs-to-ubuntu-jammy.html

Change-Id: I2c060d618bbbeaff63d506ffb00bc01750c8fcf3
diff --git a/zuul.d/xena_jobs.yaml b/zuul.d/xena_jobs.yaml
index e0a58a7..cdca20e 100644
--- a/zuul.d/xena_jobs.yaml
+++ b/zuul.d/xena_jobs.yaml
@@ -1,6 +1,7 @@
 - job:
     name: neutron-tempest-plugin-api-xena
     parent: neutron-tempest-plugin-base
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       tempest_concurrency: 4
@@ -94,6 +95,7 @@
 - job:
     name: neutron-tempest-plugin-scenario-openvswitch-xena
     parent: neutron-tempest-plugin-openvswitch
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -114,6 +116,7 @@
 - job:
     name: neutron-tempest-plugin-scenario-openvswitch-iptables_hybrid-xena
     parent: neutron-tempest-plugin-openvswitch-iptables_hybrid
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -134,6 +137,7 @@
 - job:
     name: neutron-tempest-plugin-scenario-linuxbridge-xena
     parent: neutron-tempest-plugin-linuxbridge
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -154,6 +158,7 @@
 - job:
     name: neutron-tempest-plugin-scenario-ovn-xena
     parent: neutron-tempest-plugin-ovn
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -173,6 +178,7 @@
 - job:
     name: neutron-tempest-plugin-dvr-multinode-scenario-xena
     parent: neutron-tempest-plugin-dvr-multinode-scenario
+    nodeset: openstack-two-node-focal
     override-checkout: stable/xena
     vars:
       network_api_extensions_common: *api_extensions
@@ -181,6 +187,7 @@
 - job:
     name: neutron-tempest-plugin-designate-scenario-xena
     parent: neutron-tempest-plugin-designate-scenario
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -189,6 +196,7 @@
 - job:
     name: neutron-tempest-plugin-sfc-xena
     parent: neutron-tempest-plugin-sfc
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -197,6 +205,7 @@
 - job:
     name: neutron-tempest-plugin-bgpvpn-bagpipe-xena
     parent: neutron-tempest-plugin-bgpvpn-bagpipe
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -205,6 +214,7 @@
 - job:
     name: neutron-tempest-plugin-dynamic-routing-xena
     parent: neutron-tempest-plugin-dynamic-routing
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -213,6 +223,7 @@
 - job:
     name: neutron-tempest-plugin-vpnaas-xena
     parent: neutron-tempest-plugin-vpnaas
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena
@@ -221,6 +232,7 @@
 - job:
     name: neutron-tempest-plugin-tap-as-a-service-xena
     parent: neutron-tempest-plugin-tap-as-a-service
+    nodeset: openstack-single-node-focal
     override-checkout: stable/xena
     vars:
       branch_override: stable/xena