Fixed configuration callback request data serialization; switched to jQuery for ajax call

modules/config/HttpConfigFetch.js

         console.info(
             "Send config request to " + endpoint + " for room: " + roomName);
 
-        var request = new XMLHttpRequest();
-        var error = null;
-        request.onreadystatechange = function (aEvt) {
-            if (request.readyState == 4) {
-                var status = request.status;
-                if (status === 200) {
+
+        $.ajax(
+            endpoint,
+            {
+                method: 'POST',
+                contentType: 'application/json',
+                data: JSON.stringify({"roomName": roomName}),
+                dataType: 'json',
+                error: function(jqXHR, textStatus, errorThrown) {
+                    console.error("Get config error: ", jqXHR, errorThrown)
+                    error = "Get config response status: " + textStatus;
+                    complete(false, error);
+                },
+                success: function(data, textStatus, jqXHR) {
                     try {
-                        var data = JSON.parse(request.responseText);
                         configUtil.overrideConfigJSON(
                             config, interfaceConfig, data);
                         complete(true);
                     } catch (exception) {
                         console.error("Parse config error: ", exception);
                         error = exception;
+                        complete(false, error);
                     }
-                } else {
-                    console.error("Get config error: ", request, status);
-                    error = "Get config response status: " + status;
                 }
-                complete(false, error);
             }
-        };
-
-        request.open("POST", endpoint, true);
-
-        request.setRequestHeader(
-            "Content-Type", "application/json;charset=UTF-8");
-
-        request.send({ "roomName": roomName });
+        );
     }
 };