wallet: Add abortOnClose parameter to tx sending endpoints

[nodech]

Big wallets, with lots of coins, or big transactions that needs lots of coins can take a some time to craft transactions before broadcasting. We get compounding effect when we use fundLocks where multiple requests are also queued.
So allowing new request parameter abortOnClose can work by making sure that transaction creation is done before request closes. If request closes and transaction already was being sent, it will do nothing.

#845