fix(server): clear web server close timeout on clean close

lib/server.js

@@ -213,12 +213,15 @@ var start = function(injector, config, launcher, globalEmitter, preprocess, file
     };
 
     globalEmitter.emitAsync('exit').then(function() {
-      // shutdown the server...
-      webServer.close(removeAllListeners);
-
-      // ...but don't wait forever on webServer.close() because
+      // don't wait forever on webServer.close() because
       // pending client connections prevent it from closing.
-      setTimeout(removeAllListeners, webServerCloseTimeout);
+      var closeTimeout = setTimeout(removeAllListeners, webServerCloseTimeout);
+
+      // shutdown the server...
+      webServer.close(function() {
+        clearTimeout(closeTimeout);
+        removeAllListeners();
+      });
     });
   };