Outbound message retry logic changed and environment variable added to configure amq connection

Old implementation of Customer Channel Manager to retry for messages not sent was:

• Retry until success code (200, 201) received from the outbound 3rd party API (viber, facebook or twilio). Whenever API returns any client error e.g. invalid number or missing parameter. Our retry loop is infinite because call with that message will never return success code.

New Implementation:

• Retry until API returns server error (5xx). If client error (4xx) occurs then error message will be logged in logs and on receiving success code success message will be logged.

An environment variable is added AMQ_ENABLE

• true = AMQ connection established
  - false = AMQ connection is not established
  This is added for a following scenario:
   If customer channel manager is to be used to send messages to different channels then this variable can be set to false since we don't need to establish connection to AMQ because we are using only send API.