m_amount_out was sometimes getting initialized with the sum of
an transaction's outputs, and sometimes with the sum of outputs
that were not change. This caused confusion and bugs. We now
always set it to the sum of outputs. This reverts an earlier
fix for bad amounts as this used the other semantics. The wallet
data should be converted automatically in a percentage of cases
that I'm hesitant to estimate. In any case, restoring from seed
or keys or rebuilding the cache will get it right.
