AoBuildStatus is not thread-safe, causing logspam - "Multiple build statuses for commitId"

First seen when Bamboo sends the same status multiple times in quick succession (BAM-17597). But has also been seen when Jenkins does something similar.

AoBuildStatusDao::set() calls delete() then create() with no transaction. This means it sometimes ends up as delete() delete() create() create() and multiple build statuses end up in the database.