tests/storage_pool: Support old API version on tests

Signed-off-by: hamistao <[email protected]>

integration/test_storage.py

@@ -194,6 +194,11 @@ def test_create_get_restore_delete_volume_snapshot(self):
         # Test getting all snapshots with recursion
         all_snapshots = volume.snapshots.all(use_recursion=True)
         self.assertEqual(first_snapshot, all_snapshots[0])
+        # Reponses from /1.0/storage-pools/default/volumes/custom/vol/snapshots?recursion=1 in LXD 4.0 has expires_at field as null.
+        # Setting expires_at manually to avoid breaking next check.
+        if all_snapshots[0].expires_at is None:
+            all_snapshots[1].expires_at = custom_snapshot.expires_at
+
         self.assertEqual(custom_snapshot, all_snapshots[1])
 
         # Change snapshot values