* crash test scenario
details:
Example code for inspecting nested block chain and accounts cache
database transaction framework. There seems to be a pathological
case where the system crashes after a rollback (as appeared in the
tx-pool packer code.)
* simplified crash scenario
* Workable solution (as suggested by Andri)
details:
Avoiding db.rollback() (db.commit() is OK) while vmState.stateDB is
alive.
* Rename text_txcrash => test_accounts_cache
why:
Unit tests covers part of accounts_cache handling
* comment update