Configure default container runtime in devstack

* If Kata Container is enabled, configure default runtime as
  "kata-runtime" in Zun config file.
* Update sample devstack config to document enabling kata

Change-Id: I016fd6f59a1a8b631e76f9567d5ef2e38da2bdd7

devstack/lib/zun

@@ -47,6 +47,8 @@ ZUN_CONF_DIR=/etc/zun
 ZUN_CONF=$ZUN_CONF_DIR/zun.conf
 ZUN_API_PASTE=$ZUN_CONF_DIR/api-paste.ini
 
+ENABLE_KATA_CONTAINERS=$(trueorfalse False ENABLE_KATA_CONTAINERS)
+
 CNI_BIN_DIR=/opt/cni/bin
 
 if is_ssl_enabled_service "zun" || is_service_enabled tls-proxy; then
@@ -247,6 +249,10 @@ function create_zun_conf {
         iniset $ZUN_CONF DEFAULT enabled_ssl_apis "$ZUN_ENABLED_APIS"
     fi
 
+    if [[ "$ENABLE_KATA_CONTAINERS" == "True" ]]; then
+        iniset $ZUN_CONF DEFAULT container_runtime "kata-runtime"
+    fi
+
     if is_service_enabled n-cpu; then
         iniset $ZUN_CONF compute host_shared_with_nova "True"
     fi

devstack/local.conf.sample

@@ -14,6 +14,9 @@ enable_plugin devstack-plugin-container https://opendev.org/openstack/devstack-p
 # This enables CRI plugin for containerd
 ENABLE_CONTAINERD_CRI=True
 
+# Optional:  uncomment to enable Kata Container
+# ENABLE_KATA_CONTAINERS=True
+
 # In Kuryr, KURYR_CAPABILITY_SCOPE is `local` by default,
 # but we must change it to `global` in the multinode scenario.
 KURYR_CAPABILITY_SCOPE=global

devstack/local.conf.subnode.sample

@@ -10,6 +10,9 @@ ENABLE_CONTAINERD_CRI=True
 enable_plugin devstack-plugin-container https://opendev.org/openstack/devstack-plugin-container $TARGET_BRANCH
 enable_plugin zun https://opendev.org/openstack/zun $TARGET_BRANCH
 
+# Optional:  uncomment to enable Kata Container
+# ENABLE_KATA_CONTAINERS=True
+
 KURYR_CAPABILITY_SCOPE=global
 KURYR_PROCESS_EXTERNAL_CONNECTIVITY=False
 enable_plugin kuryr-libnetwork https://opendev.org/openstack/kuryr-libnetwork $TARGET_BRANCH

devstack/settings

@@ -17,6 +17,9 @@
 # Configure Docker cluster store
 DOCKER_CLUSTER_STORE=${DOCKER_CLUSTER_STORE:-etcd://$SERVICE_HOST:$ETCD_PORT}
 
+# Enable/Disable Kata Container
+ENABLE_KATA_CONTAINERS=${ENABLE_KATA_CONTAINERS:-false}
+
 # Configure CNI plugins
 CNI_PLUGINS_INSTALL_PLUGINS=loopback,zun-cni
 CNI_PLUGINS_CONF_SOURCE_DIR=$DEST/zun/etc/cni/net.d