Allow switching the delegated validator

[p-offtermatt]

When a users validator goes out of the active set, they do not receive staking reward.
We need the Hydro contract to allow keeping the users ATOM locked, but to switch the validator that they are delegated with.

[p-offtermatt]

Is it ok if we just let people unlock if their validator falls out of the active set? seems pretty hard to manipulate