Port code to use consul

This patch is intended to preserve the
current functionality of the orchestrate module
using cosul as the backend instead of etcd.

It includes the following changes:

- each client connects to its local
etcd agent
- current_version is written to the consul kv store
- ping just checks if the local consul client is functional
- puppet/validation are tracked as checks (with failures
logged as warnings so they do not cause services to become
unregistered
- running version ported to consul kv entry