blockchain_db: match tx addition semantics to original code
blockchain_db: match tx addition semantics to original code

The original code removed key images from a tx from the blockchain
when an non to-key nor gen input was found in that tx. Additionally,
the remainder of the tx data was added to the blockchain only after
the double spend check passed.

eiabea/bitmonero,ranok/bitmonero,ranok/bitmonero,eiabea/bitmonero,eiabea/bitmonero,eiabea/bitmonero,ranok/bitmonero,ranok/bitmonero,eiabea/bitmonero,ranok/bitmonero,ranok/bitmonero,eiabea/bitmonero