Clean up INFRA_ID-worker server groups

The worker server groups don't get deleted, which can cause deployment
failues due to insufficient quota in OpenStack

Author: elfiesmelfie

destroy_cluster.sh

@@ -90,6 +90,7 @@ if [[ $FORCE == true ]]; then
     openstack security group delete "$INFRA_ID"-worker
 
     openstack server group delete "$INFRA_ID"-master
+    openstack server group delete "$INFRA_ID"-worker
 
     for c in $(openstack container list -f value); do
         echo "$c"