
Automatic merge from submit-queue Added option to specify the flannel backend, to cluster/ubuntu ```release-note ``` Generalized the cluster/ubuntu scripting so that there is a way to specify the Flannel "backend" to use. Also updated the default setting of ADMISSION_CONTROL, to match that recommended for the latest release in http://kubernetes.io/docs/admin/admission-controllers/#is-there-a-recommended-set-of-plug-ins-to-use, and updated the comment on that setting to explain it. Also made `cluster/ubuntu/reconfDocker.sh` sensitive to the `DEBUG` envar.