Change how Traffic Router gets its connectivity to TrafficOps

[jhg03a]

Currently we store credentials in the traffic router's traffic_ops.properties file. I'd like to see us add a new parameter to traffic_ops.properties for the TO API base URL similar to the rest of the TC components store that relationship.

Today, Traffic Router knows where to find TO by reading a field in the CRConfig generated by the url a user was using when performing a snapshot. That CRConfig is handed off to Traffic Router by way of Traffic Monitor. By storing the URL in the TR configs directly: you prevent connectivity issues derived from firewalls/dns-name differences at the client/TO relationship, reduce reliance on TM, and appear more consistent with the rest of Traffic Control.

[elsloo]

+1, and ideally this could be alternatively influenced via environment variables for use with things like Docker.