[Zoe] Check that invite field of makeInstance return value is an actual invite

[DavidBruant]

No check is performed on the invite field ; it is returned as it is

agoric-sdk/packages/zoe/src/zoe.js

Lines 336 to 342 in 7ceebe5

	.then(_ => installation.makeContract(contractFacet))
	.then(({ invite, publicAPI }) => {
	// Once the contract is made, we add the publicAPI to the
	// contractRecord
	instanceTable.update(instanceHandle, { publicAPI });
	return invite;
	});

Edit below by Kate 4/7:
We should add a check:

inviteIssuer.isLive(invite)
This will take another turn since isLive returns a promise.

[katelynsills]

Not doing a check isn't intentional, so this is a great issue. I think we could do:

inviteIssuer.isLive(invite)

This will take another turn since isLive returns a promise, but I think we should do it.