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/zed_jobs.yaml b/zuul.d/zed_jobs.yaml
index 097df53..43667db 100644
--- a/zuul.d/zed_jobs.yaml
+++ b/zuul.d/zed_jobs.yaml
@@ -1,6 +1,7 @@
 - job:
     name: neutron-tempest-plugin-openvswitch-zed
     parent: neutron-tempest-plugin-openvswitch
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -107,6 +108,7 @@
 - job:
     name: neutron-tempest-plugin-openvswitch-iptables_hybrid-zed
     parent: neutron-tempest-plugin-openvswitch-iptables_hybrid
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -137,6 +139,7 @@
 - job:
     name: neutron-tempest-plugin-linuxbridge-zed
     parent: neutron-tempest-plugin-linuxbridge
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -163,6 +166,7 @@
 - job:
     name: neutron-tempest-plugin-ovn-zed
     parent: neutron-tempest-plugin-ovn
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -187,6 +191,7 @@
 - job:
     name: neutron-tempest-plugin-dvr-multinode-scenario-zed
     parent: neutron-tempest-plugin-dvr-multinode-scenario
+    nodeset: openstack-two-node-focal
     override-checkout: stable/zed
     vars:
       network_api_extensions_common: *api_extensions
@@ -195,6 +200,7 @@
 - job:
     name: neutron-tempest-plugin-designate-scenario-zed
     parent: neutron-tempest-plugin-designate-scenario
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -203,6 +209,7 @@
 - job:
     name: neutron-tempest-plugin-sfc-zed
     parent: neutron-tempest-plugin-sfc
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -211,6 +218,7 @@
 - job:
     name: neutron-tempest-plugin-bgpvpn-bagpipe-zed
     parent: neutron-tempest-plugin-bgpvpn-bagpipe
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -219,6 +227,7 @@
 - job:
     name: neutron-tempest-plugin-dynamic-routing-zed
     parent: neutron-tempest-plugin-dynamic-routing
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -227,6 +236,7 @@
 - job:
     name: neutron-tempest-plugin-fwaas-zed
     parent: neutron-tempest-plugin-fwaas
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -235,6 +245,7 @@
 - job:
     name: neutron-tempest-plugin-vpnaas-zed
     parent: neutron-tempest-plugin-vpnaas
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed
@@ -243,6 +254,7 @@
 - job:
     name: neutron-tempest-plugin-tap-as-a-service-zed
     parent: neutron-tempest-plugin-tap-as-a-service
+    nodeset: openstack-single-node-focal
     override-checkout: stable/zed
     vars:
       branch_override: stable/zed