TO /deliveryservices/:id/routing makes requests to all TRs instead of by CDN

[rawlinp]

This Bug Report affects these Traffic Control components:

• Traffic Ops

Current behavior:

When a request is made to TO's GET /api/x/deliveryservices/:id/routing endpoint, TO makes a request to all TRs instead of just the TRs that belong to the same CDN as the given delivery service.

Expected behavior:

For this endpoint, TO should only make requests to TRs that belong to the CDN of the given delivery service.

Steps to reproduce:

GET /api/3.1/deliveryservices/<insert-ds-id-here>/routing

[rawlinp]

The issue is around this code:

trafficcontrol/traffic_ops/traffic_ops_golang/crstats/routing.go

Line 209 in fee39e2

func getCDNRouterFQDNs(tx *sql.Tx, requiredCDN *string) (map[tc.CDNName][]string, error) {

This API should pass a CDN name to this function instead of nil.

[srijeet0406]

@rawlinp I can take this one.