GUAC-1480: Don't set the clipboard state if it hasn't changed.

guacamole/src/main/webapp/app/client/directives/guacClient.js

@@ -414,8 +414,10 @@ angular.module('client').directive('guacClient', [function guacClient() {
 
             // Update remote clipboard if local clipboard changes
             $scope.$on('guacClipboard', function onClipboard(event, mimetype, data) {
-                if (client)
+                if (client && data !== $scope.client.clipboardData) {
                     client.setClipboard(data);
+                    $scope.client.clipboardData = data;
+                }
             });
 
             // Translate local keydown events to remote keydown events if keyboard is enabled