MySQL CB hook leaks pool options.
When you have a (prefix delegation or address) pool with options when the pool is deleted its options are not removed.
IMHO the simplest is to add a query to do that in getPools4 & co. Note we delete and recreate pools and options in subnet createUpdate so this is not a corner case.
Note in general it is pretty easy to leak an option because their parents have no cascade so they must be removed explicitly. A DELETE query with NOT EXISTS can be used to collect dangling options.
Related to #632 (closed)