avoid recreate ndb context

Signed-off-by: Javan Lacerda <[email protected]>

Author: javanlacerda

src/clusterfuzz/_internal/tests/test_libs/test_utils.py

@@ -317,6 +317,7 @@ def setUpClass(cls):
             atexit.register(_emulators[emulator_name].cleanup)
 
           if emulator_name == 'datastore':
+            cls._context_generator.__exit__(None, None, None)
             cls._context_generator = ndb_init.context()
             cls._context_generator.__enter__()