Protection against key confusion

[Drup]

The multi-connect issue is fixed, but it is still possible to have multiple connects by using keys. If you have two ethernet devices, eth1 and eth2, that both have a key and you point to the same interface on the command line, it's going to crash.

I think this issue is inherent to how key works, and it's difficult to know if it's valid to have the same key twice without adding semantics to the keys, which we avoided in functoria.

The obvious solution is to make the various connect resilient to multi-connects, but since this seems difficult, maybe introducing some memoisation somewhere would help ?