Remove unused metron_endpoint.dropsonde_port property

- Remove unused BOSH property and associated config field from traffic
  controller
- Pass GRPCAddress rather than UDPAddress when creating a test server.
  gRPC-Go v1.52.0+ will error if the provided endpoint is empty:
  grpc/grpc-go#5732

(cherry picked from commit 63cf49e)

jobs/loggregator_trafficcontroller/spec

@@ -88,9 +88,6 @@ properties:
   metron_endpoint.host:
     description: "The host used to emit messages to the Metron agent"
     default: "127.0.0.1"
-  metron_endpoint.dropsonde_port:
-    description: "The port used to emit dropsonde messages to the Metron agent"
-    default: 3457
   metron_endpoint.grpc_port:
     description: "The port used to emit grpc messages to the Metron agent"
     default: 3458

jobs/loggregator_trafficcontroller/templates/bpm.yml.erb

@@ -28,7 +28,6 @@ processes:
   - name: loggregator_trafficcontroller
     executable: /var/vcap/packages/loggregator_trafficcontroller/trafficcontroller
     env:
-      AGENT_UDP_ADDRESS: "<%= p('metron_endpoint.host').to_s + ":" + p('metron_endpoint.dropsonde_port').to_s %>"
       AGENT_GRPC_ADDRESS: "<%= p('metron_endpoint.host').to_s + ":" + p('metron_endpoint.grpc_port').to_s %>"
 
       ROUTER_ADDRS: "<%= router_addrs.join(",") %>"

src/testservers/traffic_controller.go

@@ -37,7 +37,7 @@ func BuildTrafficControllerConf(routerAddr string, agentPort int, logCacheAddr s
 			ServerName: "cloud-controller",
 		},
 		Agent: tcConf.Agent{
-			UDPAddress: fmt.Sprintf("localhost:%d", agentPort),
+			GRPCAddress: fmt.Sprintf("localhost:%d", agentPort),
 		},
 		GRPC: tcConf.GRPC{
 			CertFile: LoggregatorTestCerts.Cert("trafficcontroller"),

src/trafficcontroller/app/config.go

@@ -10,7 +10,6 @@ import (
 
 // Agent stores configuration for communication to a logging/metric agent.
 type Agent struct {
-	UDPAddress  string `env:"AGENT_UDP_ADDRESS"`
 	GRPCAddress string `env:"AGENT_GRPC_ADDRESS"`
 }