[RPC] Adding required fields to the RegisterDriver RPC call.

rpc/protos/erdos_scheduler.proto

@@ -73,6 +73,10 @@ message RegisterDriverRequest {
 message RegisterDriverResponse {
     bool success = 1;
     string message = 2;
+    // The following fields are used to communicate the worker that the driver
+    // has been scheduled on.
+    string worker_name = 3;
+    string worker_id = 4;
 }
 
 /// Application related RPC structures.