Default values and options for backup operations, such as
backup_namespace, restore_namespace and backup_runner_options,
are already defined in code.
Specific per database values should be defined in the datastore
sections, their presence in the DEFAULT is deprecated and can
cause confusion and generate errors and conflicts.
We should remove these specific values and leave only the
default common storage strategy and storage options for backups.
Change-Id: Iaf4a316087a1d2bd66c80206fb5b5c344b49ec7e
2d2fa6ab8a