We were missing a test that would exercise trx_free_prepared()
with innodb_fast_shutdown=0. Add a test.
Note: if shutdown hangs due to the XA PREPARE transactions,
in MariaDB 10.2 the test would unfortunately pass, but take
2*60 seconds longer, because of two shutdown_server statements
timing out after 60 seconds. Starting with MariaDB 10.3, the
hung server would be killed with SIGABRT, and the test could
fail thanks to a backtrace message.
The test innodb.recovery_shutdown would occasionally fail,
because recovered incomplete transactions would be conflicting
with DROP TABLE, causing the background drop table queue to be invoked.
Add a slow shutdown before dropping the tables, so that the
recovered transactions will be rolled back. Starting with MDEV-14705,
normal shutdown would abort the rollback of recovered transactions.
row_undo_step(), trx_rollback_active(): Abort the rollback of a
recovered ordinary transaction if fast shutdown has been initiated.
trx_rollback_resurrected(): Convert an aborted-rollback transaction
into a fake XA PREPARE transaction, so that fast shutdown can proceed.
trx_rollback_resurrected(): If shutdown was initiated, fake all
remaining active transactions to XA PREPARE state, so that shutdown
can proceed. Also, make the parameter "all" an output that will be
assigned to FALSE in this case.
trx_rollback_or_clean_recovered(): Remove the shutdown check
(it was moved to trx_rollback_resurrected()).
trx_undo_free_prepared(): Relax assertions.
