[tests] check v0.17.1 and v0.18.1 backwards compatibility

test/functional/test_runner.py

@@ -158,6 +158,7 @@ BASE_SCRIPTS = [
     'feature_assumevalid.py',
     'example_test.py',
     'wallet_txn_doublespend.py',
+    'feature_backwards_compatibility.py',
     'wallet_txn_clone.py --mineblock',
     'feature_notifications.py',
     'rpc_getblockfilter.py',