Update "containerpilot.json" to assume "consul" if "CONSUL" is unset

This mimics the behavior of the Python code:

    bin/manage.py:19:consul = pyconsul.Consul(host=os.environ.get('CONSUL', 'consul'))

This allows us to remove `CONSUL=consul` from the Compose files, thus allowing for local deploys to assume the correct value, and Triton deploys to use CNS via `_env` to set `CONSUL=...` to an appropriate value.

Author: tianon

etc/containerpilot.json

@@ -1,5 +1,5 @@
 {
-  "consul": "{{ .CONSUL }}:8500",
+  "consul": "{{ if .CONSUL }}{{ .CONSUL }}{{ else }}consul{{ end }}:8500",
   "preStart": "python /usr/local/bin/manage.py",
   "preStop": "python /usr/local/bin/manage.py pre_stop",
   "services": [

local-compose.yml

@@ -7,8 +7,6 @@ services:
         mem_limit: 512m
         build: .
         env_file: _env
-        environment:
-            - CONSUL=consul
         ports:
             - 27017