Change root node for created submissions to data

By default XLSForms set the default node to 'data'

onadata/apps/api/tests/viewsets/test_xform_submission_viewset.py

@@ -556,6 +556,16 @@ def test_rapidpro_post_submission(self):
         self.assertContains(response, 'Successful submission', status_code=201)
         self.assertTrue(response.has_header('Date'))
         self.assertEqual(response['Location'], 'http://testserver/submission')
+        # InstanceID is returned as uuid:<uuid>
+        # Retrieving the uuid without the prefix in order to retrieve
+        # the actual instance
+        uuid = response.data.get('instanceID').split(':')[1]
+        instance = Instance.objects.get(uuid=uuid)
+        expected_xml = (
+            "<?xml version='1.0' ?><data id="
+            "'transportation_2011_07_25'><fruit_name>orange"
+            "</fruit_name></data>")
+        self.assertEqual(instance.xml, expected_xml)
 
     def test_legacy_rapidpro_post_submission(self):
         """

onadata/libs/serializers/data_serializer.py

@@ -46,7 +46,7 @@ def create_submission(request, username, data_dict, xform_id):
     """
     Returns validated data object instances
     """
-    xml_string = dict2xform(data_dict, xform_id)
+    xml_string = dict2xform(data_dict, xform_id, root='data')
     xml_file = BytesIO(xml_string.encode('utf-8'))
 
     error, instance = safe_create_instance(username, xml_file, [], None,