Add MESOS_DOCKER_DUMP_LOGS to enforce log dumping

cluster/mesos/docker/util.sh

@@ -317,6 +317,9 @@ function validate-cluster {
 
 # Delete a kubernetes cluster
 function kube-down {
+  if [ "${MESOS_DOCKER_DUMP_LOGS:-false}" == "true" ]; then
+    cluster::mesos::docker::dump_logs "${MESOS_DOCKER_WORK_DIR}/log"
+  fi
   echo "Stopping ${KUBERNETES_PROVIDER} cluster" 1>&2
   # Since restoring a stopped cluster is not yet supported, use the nuclear option
   cluster::mesos::docker::docker_compose kill