Returning DB_SUCCESS unconditionally if !trx->lock.wait_lock in
lock_trx_handle_wait() is wrong. Because even if
trx->lock.was_chosen_as_deadlock_victim was not set before the first check
in lock_trx_handle_wait(), it can be set after
the check, and trx->lock.wait_lock can be reset by another thread from
lock_reset_lock_and_trx_wait() if the transaction was chosen as deadlock
victim. In this case lock_trx_handle_wait() will return DB_SUCCESS even
the transaction was marked as deadlock victim, and continue execution
instead of rolling back.

The fix is to check trx->lock.was_chosen_as_deadlock_victim once more if
trx->lock.wait_lock is reset, as trx->lock.wait_lock can be reset only
after trx->lock.was_chosen_as_deadlock_victim was set if the transaction
was chosen as deadlock victim.