Dual block replay during conversion moves incorrect number of leaves

[gballet]

Because the CurrentAccountAddress variable is unique, and stored in the statedb, if for whatever reason a block at a given height is re-executed, there will be an issue because the head will have moved. This will produce an incorrect converted hash.

In order to do this, the value of the iterator at a given block has to be stored and recoverable.

[gballet]

fixed by #304