Fix gen_statem:reply/2 bug in emqx_client module

Prior to this change, the arguments passed to gen_statem:reply is bad
args, first arg should be a tuple, but it is a pid. So it would
trigger crash.

This change fix this bug.

src/emqx_client.erl

@@ -1049,7 +1049,7 @@ timeout_calls(Timeout, Calls) ->
 timeout_calls(Now, Timeout, Calls) ->
     lists:foldl(fun(C = #call{from = From, ts = Ts}, Acc) ->
                     case (timer:now_diff(Now, Ts) div 1000) >= Timeout of
-                        true  -> gen_statem:reply(From, {error, ack_timeout}),
+                        true  -> From ! {error, ack_timeout},
                                  Acc;
                         false -> [C | Acc]
                     end
@@ -1231,4 +1231,3 @@ bump_last_packet_id(State = #state{last_packet_id = Id}) ->
 -spec next_packet_id(packet_id()) -> packet_id().
 next_packet_id(?MAX_PACKET_ID) -> 1;
 next_packet_id(Id) -> Id + 1.
-