This is a regression due to MDEV-17816.
When creating a table fails, we must roll back the dictionary
transaction. Because the rollback may rename tables, and because
InnoDB lacks proper undo logging for CREATE operations, we must
drop the incompletely created table before rolling back the
transaction, which could include a RENAME operation.
But, we must not blindly drop the table by name; after all,
the operation could have failed because another table by the
same name already existed.
create_table_info_t::m_drop_before_rollback: A flag that is set
if the table needs to be dropped before transaction rollback.
create_table_info_t::create_table(): Remove some duplicated
error handling.
ha_innobase::create(): On error, only drop the table if it was
actually created.
