DELETE IGNORE should not ignore deadlocks (again)

This is basically a duplicate or a reincarnation of MDEV-117. For some reason, the test innodb.mdev-117 started failing in 10.2.

It is uncertain when this test started failing. The test is nondeterministic, because there is a race condition between the concurrently executing DELETE IGNORE and DELETE statements.

When a deadlock is reported for DELETE IGNORE, the SQL layer would call handler::print_error() but then proceed to the next row, as if no error had happened (which is the purpose of DELETE IGNORE). So, when it proceeded to handler::ha_rnd_next(), InnoDB would hit an assertion failure, because the transaction no longer exists, and we are not executing at the start of a statement.