Change `report_defunct_voter` so that it doesn't pay to make bad votes.

[gavofyork]

In order to ensure that Governance proxies cannot drain accounts, it's important to avoid any governance operations which can result in funds being reserved and slashed and that the weight system is used to charge the calling account for frivolous computation.

vote should be refactored so that it reserves the "right" amount of a deposit, and report_defunct_voter should be redone so that the correct (or at least maximum) amount of weight is charged-for up front. The deposit can be returned to the original account in the success case, and no further action taken in the case of no success.