set default docker storage driver to devicemapper and fix DOCKER_OPTS passing

cluster/centos/minion/scripts/docker.sh

@@ -20,7 +20,7 @@ DOCKER_OPTS=${1:-""}
 DOCKER_CONFIG=/opt/kubernetes/cfg/docker
 
 cat <<EOF >$DOCKER_CONFIG
-DOCKER_OPTS="-H tcp://127.0.0.1:4243 -H unix:///var/run/docker.sock --selinux-enabled=false ${DOCKER_OPTS}"
+DOCKER_OPTS="-H tcp://127.0.0.1:4243 -H unix:///var/run/docker.sock -s devicemapper --selinux-enabled=false ${DOCKER_OPTS}"
 EOF
 
 cat <<EOF >/usr/lib/systemd/system/docker.service

cluster/centos/util.sh

@@ -274,7 +274,7 @@ function provision-minion() {
     echo "chmod -R +x /opt/kubernetes/bin"
 
     echo "bash ${KUBE_TEMP}/minion/scripts/flannel.sh ${ETCD_SERVERS} ${FLANNEL_NET}"
-    echo "bash ${KUBE_TEMP}/minion/scripts/docker.sh ${DOCKER_OPTS}"
+    echo "bash ${KUBE_TEMP}/minion/scripts/docker.sh \"${DOCKER_OPTS}\""
     echo "bash ${KUBE_TEMP}/minion/scripts/kubelet.sh ${master_ip} ${minion_ip}"
     echo "bash ${KUBE_TEMP}/minion/scripts/proxy.sh ${master_ip}"