Release plus servicer when queuing a transaction statement

When we receive multiple concurrent requests for a transaction we queue them to be processed serially in the transaction's queue.  We're supposed to release the servicer that was occupied with the task of adding to the transaction queue when we queue for the transaction but aren't.  This means we're reserving a servicer whilst waiting which isn't intended since the one active request for the transaction will wake a waiter and "hand over" its servicer.