Bug #30767 AUTO_INCREMENT on rollback

Description:
When you perform a rollback, the Auto Incremented index is not rolled back. This may actually not be a bug, it may be designed that way, but the index is spent and cannot be found in the table. It's not a big deal for me, but it can be for others.

How to repeat:
Create a table with an AUTO_INCREMENT index. The table must be of engine InnoDB. Write a script with SQL BEGIN and SQL COMMIT but force a rollback.

Suggested fix:
Rollback the auto incremented index.

This is the defined behavior, we guarantee that each auto_increment id that is handed out is greater than all previous ones. There is no (ant can't be) any guarantee that it is gapless at the same time.

So once an auto_increment value is taken by a transaction all following transactions have to get a value larger than that, and if the first transaction is rolled back the value is lost.