Enable containerized storage plugins mounter on GCI

This reverts commit 765f7b9406.

cluster/gce/gci/configure-helper.sh

@@ -473,6 +473,7 @@ function start-kubelet {
   flags+=" --cluster-dns=${DNS_SERVER_IP}"
   flags+=" --cluster-domain=${DNS_DOMAIN}"
   flags+=" --config=/etc/kubernetes/manifests"
+  flags+=" --experimental-mounter-path=${KUBE_HOME}/bin/mounter"
 
   if [[ -n "${KUBELET_PORT:-}" ]]; then
     flags+=" --port=${KUBELET_PORT}"
@@ -1171,6 +1172,10 @@ function override-kubectl {
     echo "export PATH=${KUBE_HOME}/bin:\$PATH" > /etc/profile.d/kube_env.sh
 }
 
+function pre-warm-mounter {
+    ${KUBE_HOME}/bin/mounter &> /dev/null
+}
+
 ########### Main Function ###########
 echo "Start to configure instance for kubernetes"
 
@@ -1205,6 +1210,8 @@ else
 fi
 
 override-kubectl
+# Run the containerized mounter once to pre-cache the container image.
+pre-warm-mounter
 assemble-docker-flags
 load-docker-images
 start-kubelet