Switch to cirros uec image in multinode jobs

Kernel panic is seen in these jobs as well,
let's switch to cirros uec image to avoid it.

singlenode jobs already switched with
https://review.opendev.org/q/Ic57f828c08f1793226759baedb3eb2f646191e1f.

Change-Id: I34f3bbf7d30ddce23758ffb513abff0500b1fad6

zuul.d/tempest-multinode.yaml

@@ -39,6 +39,9 @@
     vars:
       tox_envlist: integrated-network
       devstack_localrc:
+        CIRROS_VERSION: 0.5.1
+        DEFAULT_IMAGE_NAME: cirros-0.5.1-x86_64-uec
+        DEFAULT_IMAGE_FILE_NAME: cirros-0.5.1-x86_64-uec.tar.gz
         Q_ML2_TENANT_NETWORK_TYPE: vxlan
         Q_ML2_PLUGIN_MECHANISM_DRIVERS: openvswitch,linuxbridge
         Q_AGENT: openvswitch
@@ -169,6 +172,9 @@
     vars:
       tox_envlist: integrated-network
       devstack_localrc:
+        CIRROS_VERSION: 0.5.1
+        DEFAULT_IMAGE_NAME: cirros-0.5.1-x86_64-uec
+        DEFAULT_IMAGE_FILE_NAME: cirros-0.5.1-x86_64-uec.tar.gz
         Q_ML2_TENANT_NETWORK_TYPE: vxlan
         Q_ML2_PLUGIN_MECHANISM_DRIVERS: openvswitch,linuxbridge
         Q_AGENT: openvswitch
@@ -254,6 +260,9 @@
       devstack_plugins:
         neutron: https://opendev.org/openstack/neutron.git
       devstack_localrc:
+        CIRROS_VERSION: 0.5.1
+        DEFAULT_IMAGE_NAME: cirros-0.5.1-x86_64-uec
+        DEFAULT_IMAGE_FILE_NAME: cirros-0.5.1-x86_64-uec.tar.gz
         Q_ML2_TENANT_NETWORK_TYPE: vxlan
         Q_ML2_PLUGIN_MECHANISM_DRIVERS: openvswitch,linuxbridge
         Q_AGENT: openvswitch
@@ -368,6 +377,9 @@
             ovn:
               enable_distributed_floating_ip: True
       devstack_localrc:
+        CIRROS_VERSION: 0.5.1
+        DEFAULT_IMAGE_NAME: cirros-0.5.1-x86_64-uec
+        DEFAULT_IMAGE_FILE_NAME: cirros-0.5.1-x86_64-uec.tar.gz
         Q_AGENT: ovn
         ML2_L3_PLUGIN: ovn-router,trunk
         Q_ML2_PLUGIN_MECHANISM_DRIVERS: ovn,logger