Fixes#1212.
Before this commit, transactions were kept monitored in
WalletService.transaction_monitor after first being seen, only if the
list of confirmed callbacks was non empty, but this meant that the logic
is process_new_tx was not executed, meaning the height field of the utxo
was never updated from INF_HEIGHT, so the utxo would continue to be seen
as having zero confirmations, even after blocks are mined.
After this commit, we add any transaction that was seen to the
active_txs dict, so that the height field, and thus the number of
confirmations reported, is correct even if the caller never registered a
confirmed callback.
Adam Gibson
09b9747819