- introduce block and simplify when conditions
- introduce config.yml so the self-standing etcd role can be run (e.g. to test etcd cluster deployment)
- remove empty task files
- skip dependency on openshift_etcd_ca
- replace cert paths with their appropriate variables

Includes bash functions for etcdctl2 and etcdctl3 which provide reasonable
defaults for etcdctl functions on a host that's configured with openshift_etcd.