vdk-core: fix buggy (false positive) connection unit test

We have a unit test that checks the raw (or native) connection is being
saved properly - but the test was buggy since they are qual in a sense
they have the same attribute values (as there's only one "is_valid") .
But we care if it's the same instance. So we switch to "is"

Testing Done: After changing == to "is" ran the test and it failed (as
it should) and then fix the test.

Signed-off-by: Antoni Ivanov <[email protected]>

projects/vdk-core/tests/vdk/internal/builtin_plugins/connection/test_connection_router.py

@@ -45,7 +45,7 @@ def test_router_raw_connection():
     router.add_open_connection_factory_method("RAW_DB", lambda: mock_conn)
 
     conn = router.open_connection("RAW_DB")
-    assert mock_conn == conn.connect()
+    assert mock_conn is conn._connect()
 
 
 def test_router_open_connection_closed():