COOK-2618 - Fixing myisam-recover option

Changed name to use hyphen instead of underscore as that's the official
way.

http://dev.mysql.com/doc/refman/5.0/en/server-options.html#option_mysqld_myisam-recover

Removing duplicate from attribute file.

Setting option in [mysqld] section of option file to use attibute
instead of being hard coded.