Make sure we never have 2 kuryr-controllers

This commit adds constraints preventing 2 kuryr-controllers from being
created in non-HA deployments running on K8s when doing an update of the K8s
Deployment (e.g. when upgrading the kuryr-controller image).

Change-Id: Ic5fe9aa9e63f2bee51d85e112d543e6955ab3bc8
Closes-Bug: 1802099

devstack/lib/kuryr_kubernetes

@@ -522,6 +522,21 @@ metadata:
   namespace: kube-system
 spec:
   replicas: ${KURYR_CONTROLLER_REPLICAS:-1}
+EOF
+
+    # When running without HA we should make sure that we won't have more than
+    # one kuryr-controller pod in the deployment.
+    if [ "$controller_ha" == "False" ]; then
+        cat >> "${output_dir}/controller_deployment.yml" << EOF
+  strategy:
+    type: RollingUpdate
+    rollingUpdate:
+      maxSurge: 0
+      maxUnavailable: 1
+EOF
+    fi
+
+    cat >> "${output_dir}/controller_deployment.yml" << EOF
   template:
     metadata:
       labels: