Add more info during rabbitmqctl shutdown

We want to know at which shutdown stage the command is at, and get
confirmation of successful shutdown.

Inform is used all over the place, is it OK to remove " ..." from all
rabbitmqctl commands that use it?

[#142699191]

Author: gerhard

src/rabbit_control_main.erl

@@ -156,7 +156,7 @@ start() ->
               Inform = case Quiet of
                            true  -> fun (_Format, _Args1) -> ok end;
                            false -> fun (Format, Args1) ->
-                                            io:format(Format ++ " ...~n", Args1)
+                                            io:format(Format ++ "~n", Args1)
                                     end
                        end,
               try
@@ -271,17 +271,20 @@ do_action(Command, Node, Args, Opts, Inform, Timeout) ->
     end.
 
 shutdown_node_and_wait_pid_to_stop(Node, Pid, Inform) ->
-    Inform("Shutting down RabbitMQ node ~p running at PID ~p", [Node, Pid]),
     Res = call(Node, {rabbit, stop_and_halt, []}),
     case Res of
-        ok -> wait_for_process_death(Pid);
+        ok ->
+            Inform("Waiting for PID ~s to terminate", [Pid]),
+            wait_for_process_death(Pid),
+            Inform("RabbitMQ node running at PID ~s successfully shut down", [Pid]);
         _  -> ok
     end,
     Res.
 
 action(shutdown, Node, [], _Opts, Inform) ->
     case rpc:call(Node, os, getpid, []) of
         Pid when is_list(Pid) ->
+            Inform("Shutting down RabbitMQ node ~p running at PID ~s", [Node, Pid]),
             shutdown_node_and_wait_pid_to_stop(Node, Pid, Inform);
         Error -> Error
     end;