Update TO routing APIs to use Traffic Stats data (InfluxDB)

Dependent on TC-536

Currently the routing endpoint in Traffic Ops (apis/1.2/cdns/routing, api/1.2/deliveryservices/:id/routing.json) reach out to the crs/stats API on one Traffic Router to get the information. Traffic Routers are stateless therefore the crs/stats API data from one traffic router is not a full picture. Once TC-536 is complete the routing APIs in Traffic Ops should be updated to use the data that is stored by Traffic Stats in InfluxDB.