Configure cluster for e2e tests.

When KUBE_E2E_STORAGE_TEST_ENVIRONMENT is set to 'true', kube-up.sh script
will:

- Install the right packages for all storage volumes.
- Use devicemapper as docker storage backend. 'aufs', the default one on
Debian, does not support extended attibutes required by Ceph RBD and Gluster
server containers.

Tested on GCE and Vagrant, e2e tests for storage volumes passes without any
additional configuration.

cluster/saltbase/salt/docker/docker-defaults

@@ -1,3 +1,7 @@
 {% set grains_opts = grains.get('docker_opts', '') -%}
-DOCKER_OPTS="{{grains_opts}} --bridge=cbr0 --iptables=false --ip-masq=false --log-level=warn"
+{% set e2e_opts = '' -%}
+{% if pillar.get('e2e_storage_test_environment', '').lower() == 'true' -%}
+{% set e2e_opts = '-s devicemapper' -%}
+{% endif -%}
+DOCKER_OPTS="{{grains_opts}} {{e2e_opts}} --bridge=cbr0 --iptables=false --ip-masq=false --log-level=warn"
 DOCKER_NOFILE=1000000