Set default ecomworker broker host to 127.0.0.1

Fix #21

Cherry picked from 31b6ee56028550b9aa9fac840f3f2040fadaeaf2

playbooks/edx_sandbox.yml

@@ -55,6 +55,7 @@
     - role: ecommerce
       when: SANDBOX_ENABLE_ECOMMERCE
     - role: ecomworker
+      ECOMMERCE_WORKER_BROKER_HOST: 127.0.0.1
       when: SANDBOX_ENABLE_ECOMMERCE
     - programs
     - analytics_api

playbooks/vagrant-devstack.yml

@@ -33,7 +33,8 @@
     - elasticsearch
     - forum
     - ecommerce
-    - ecomworker
+    - role: ecomworker
+      ECOMMERCE_WORKER_BROKER_HOST: 127.0.0.1
     - programs
     - role: notifier
       NOTIFIER_DIGEST_TASK_INTERVAL: "5"