Change the default dir for loading xml files.

This should always be overridden by the testcases if needed.

lms/envs/test.py

@@ -15,8 +15,9 @@ sessions. Assumes structure:
 from .common import *
 import os
 from path import path
-from warnings import filterwarnings, simplefilter
+from tempfile import mkdtemp
 from uuid import uuid4
+from warnings import filterwarnings, simplefilter
 
 # mongo connection settings
 MONGO_PORT_NUM = int(os.environ.get('EDXAPP_TEST_MONGO_PORT', '27017'))
@@ -136,7 +137,7 @@ update_module_store_settings(
         'fs_root': TEST_ROOT / "data",
     },
     xml_store_options={
-        'data_dir': COMMON_TEST_DATA_ROOT,
+        'data_dir': mkdtemp(),  # never inadvertently load all the XML courses
     },
     doc_store_settings={
         'host': MONGO_HOST,