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/yoga_jobs.yaml b/zuul.d/yoga_jobs.yaml
index bc88c83..7d3c36d 100644
--- a/zuul.d/yoga_jobs.yaml
+++ b/zuul.d/yoga_jobs.yaml
@@ -1,6 +1,7 @@
 - job:
     name: neutron-tempest-plugin-api-yoga
     parent: neutron-tempest-plugin-base
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       tempest_concurrency: 4
@@ -96,6 +97,7 @@
 - job:
     name: neutron-tempest-plugin-scenario-openvswitch-yoga
     parent: neutron-tempest-plugin-openvswitch
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -116,6 +118,7 @@
 - job:
     name: neutron-tempest-plugin-scenario-openvswitch-iptables_hybrid-yoga
     parent: neutron-tempest-plugin-openvswitch-iptables_hybrid
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -136,6 +139,7 @@
 - job:
     name: neutron-tempest-plugin-scenario-linuxbridge-yoga
     parent: neutron-tempest-plugin-linuxbridge
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -156,6 +160,7 @@
 - job:
     name: neutron-tempest-plugin-scenario-ovn-yoga
     parent: neutron-tempest-plugin-ovn
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -177,6 +182,7 @@
 - job:
     name: neutron-tempest-plugin-dvr-multinode-scenario-yoga
     parent: neutron-tempest-plugin-dvr-multinode-scenario
+    nodeset: openstack-two-node-focal
     override-checkout: stable/yoga
     vars:
       network_api_extensions_common: *api_extensions
@@ -185,6 +191,7 @@
 - job:
     name: neutron-tempest-plugin-designate-scenario-yoga
     parent: neutron-tempest-plugin-designate-scenario
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -193,6 +200,7 @@
 - job:
     name: neutron-tempest-plugin-sfc-yoga
     parent: neutron-tempest-plugin-sfc
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -201,6 +209,7 @@
 - job:
     name: neutron-tempest-plugin-bgpvpn-bagpipe-yoga
     parent: neutron-tempest-plugin-bgpvpn-bagpipe
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -209,6 +218,7 @@
 - job:
     name: neutron-tempest-plugin-dynamic-routing-yoga
     parent: neutron-tempest-plugin-dynamic-routing
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -217,6 +227,7 @@
 - job:
     name: neutron-tempest-plugin-vpnaas-yoga
     parent: neutron-tempest-plugin-vpnaas
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga
@@ -225,6 +236,7 @@
 - job:
     name: neutron-tempest-plugin-tap-as-a-service-yoga
     parent: neutron-tempest-plugin-tap-as-a-service
+    nodeset: openstack-single-node-focal
     override-checkout: stable/yoga
     vars:
       branch_override: stable/yoga