Failed commit not properly rolled back

[Bixilon]

Sometimes when committing a transaction (https://github.com/blackbeam/mysql_async/blob/master/src/queryable/transaction.rs#L179), it commit fails because of a mysql deadlock. When this happens you must explicitly rollback the changes, otherwise when creating a new transaction it will be nested.

This is checked in the code, but somehow it does not work and I could not find any tests in it.

I must wrap my code from

        trx.commit().await.map(|_| result).map_err(Into::into)

to

        match trx.commit().await {
            Ok(_) => {
                Ok(result)
            },
            Err(e) => {
                conn.query_drop("ROLLBACK;").await?;
                Err(e.into())
            }
        }

See stalwartlabs/stalwart#1271 for more details.

Can you please fix this?

Thank you!