[scripts][worker] Use WorkController constants and use send as they are bytes now

beat/core/scripts/worker.py

@@ -150,7 +150,7 @@ def connect_to_scheduler(address, name):
     poller.register(socket, zmq.POLLIN)
 
     # Tell the scheduler we are ready
-    socket.send_string('rdy')
+    socket.send(WorkerController.READY)
 
     # Wait for a response from the scheduler
     logger.info("Waiting for the scheduler...")
@@ -419,7 +419,7 @@ def main(user_input=None):
 
 
     if socket:
-        socket.send_string(WorkerController.EXIT)
+        socket.send(WorkerController.EXIT)
 
 
     # Cleanup