Add REST (un)assign tag tests (#1898)

Signed-off-by: Marinov Avgustin <Avgustin.Marinov@bosch.com>

hawkbit-rest/hawkbit-rest-core/src/test/java/org/eclipse/hawkbit/rest/util/JsonBuilder.java

@@ -52,9 +52,8 @@ public abstract class JsonBuilder {
     public static String controllerIds(final Collection<String> ids) throws JSONException {
         final JSONArray list = new JSONArray();
         for (final String smID : ids) {
-            list.put(new JSONObject().put("controllerId", smID));
+            list.put(smID);
         }
-
         return list.toString();
     }