fix(emqx_connection): do not raise an exception for normal shutdown

apps/emqx/src/emqx_connection.erl

@@ -680,6 +680,12 @@ maybe_raise_exception(#{
     stacktrace := Stacktrace
 }) ->
     erlang:raise(Exception, Context, Stacktrace);
+maybe_raise_exception({shutdown, normal}) ->
+    ok;
+maybe_raise_exception(normal) ->
+    ok;
+maybe_raise_exception(shutdown) ->
+    ok;
 maybe_raise_exception(Reason) ->
     exit(Reason).