Fix AcceptTransactionSet Deadlocks

We changed the locking conventions around AcceptTransactionSet to more formally match the conventions around the rest of the exported functions in the codebase, unfortunately this introduced some deadlocks that hadn't been there previously. These deadlocks are not active in v1.1.0, but were made active I think only a day or two later.

Bottom line is, these deadlocks did not make it into a release but they have been in master and I know a few people have been using the master branch.