At #1616 I added a Symbol.for('getInterfaceGuard') meta method to all exo objects, so that clients could ask for their alleged interface guard.

At https://github.com/Agoric/agoric-sdk/actions/runs/5273958254/jobs/9538043185?pr=7926#step:5:455 we see one of several places where agoric-sdk tests fail when linked to current endo as a result.

Used Agoric/agoric-sdk#7926 to detect such problems