fix(web-server): implement a timeout on webServer.close()

Closes #952

lib/server.js

@@ -190,6 +190,7 @@ var start = function(injector, config, launcher, globalEmitter, preprocess, file
     });
   }
 
+  var webServerCloseTimeout = 3000;
   var disconnectBrowsers = function(code) {
     // Slightly hacky way of removing disconnect listeners
     // to suppress "browser disconnect" warnings
@@ -199,16 +200,28 @@ var start = function(injector, config, launcher, globalEmitter, preprocess, file
       sockets[key].removeAllListeners('disconnect');
     });
 
+    var removeAllListenersDone = false;
+    var removeAllListeners = function() {
+      // make sure we don't execute cleanup twice
+      if (removeAllListenersDone) {
+        return;
+      }
+      removeAllListenersDone = true;
+      webServer.removeAllListeners();
+      processWrapper.removeAllListeners();
+      done(code || 0);
+    };
+
     globalEmitter.emitAsync('exit').then(function() {
-      webServer.close(function() {
-        webServer.removeAllListeners();
-        processWrapper.removeAllListeners();
-        done(code || 0);
-      });
+      // shutdown the server...
+      webServer.close(removeAllListeners);
+
+      // ...but don't wait forever on webServer.close() because
+      // pending client connections prevent it from closing.
+      setTimeout(removeAllListeners, webServerCloseTimeout);
     });
   };
 
-
   try {
     processWrapper.on('SIGINT', disconnectBrowsers);
     processWrapper.on('SIGTERM', disconnectBrowsers);