specify the cdr category for xml_cdr (#7046)

* update xml_cdr with the latest changes to the maintenance application
Update the public static function database_maintenance in xml_cdr
class to use the newest changes in the maintenance class. Constants are
now defined in the class for the table names and subcategories.

* update app_config file with necessary default setting changes

* remove constants

* use empty instead of null check

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Co-authored-by: Tim Fry <[email protected]>