Reset the result types, clearing zero_type
Search.Database.MySQL: Don't used DELAYED queries.

The DELAYED query modifier is:

  * Not supported with InnoDB tables. This causes failures with
    MySQL versions (eg 5.5) where InnoDB (and not MyISAM) is default.

  * Ignored in MySQL 5.6.

  * Deprecated in MySQL 5.6.6.

Fixes [bug 7255].