Change rules can be circumvented by re-registering keys on a new chain

[mjbrisebois]

Discovered when writing the scenario for claiming unmanaged keys (see e1bd416).

Reproduction steps

1. A key is registered (managed or unmanaged) on chain A
2. The same key is registered again on chain B
3. Chain B can revoke the key without knowing the revocation keys of chain A's change rules

Since key anchors can only contain the key bytes, there is no way to determine which chain's change rules should be enforced.

[mjbrisebois]

Will be solved in Holochain by adding key_authority to the agent commit actions.