Bugfixes: fix rebroadcast_pending loop and invalid recent registrations

Two fixes in here; first is the rebroadcast_pending loop, which was
never being started, so if a transaction wasn't disseminated in its
initial send for some reason, it would hang forever. The loop is now
started correctly. I believe this addresses the stuck transactions
bug mentioned in Issue #575

Second, a minor issue in how I allocated the vector of recent account
registrations caused the vector to have a slew of nonsense accounts in
it. This is now fixed.