queue: add work-around for https://github.com/killbill/killbill/issues/223

Use C-style comment to drop the LAST_INSERT_ID argument on H2.
This makes the queue code less robust on H2, but it should only be used on MySQL
in production anyway for now.

See http://dev.mysql.com/doc/refman/5.1/en/comments.html.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>