[Tarantool-patches] [PATCH 1/1] applier: send heartbeat not only on commit, but on any write

[Vladislav Shpilevoy]

Appeared the transactions leak afterwards anyway.

The problem was that txn->fiber was not set to NULL for
regular async transactions anywhere in applier. So they all
leaked.

I made applier on_commit/on_rollback triggers nullify txn->fiber
so it could be freed when commit/rollback are done.