Keep "Storage" legacy permission granted.

We're willing to grant STORAGE_PERMISSIONS, but that set will become
empty once isolated storage is enabled.  To keep legacy apps happy,
grant them at least one of the new split permissions, so they think
they hold the "Storage" permission.

Bug: 124224798
Test: manual
Change-Id: I306fc9fd223d0b720cd7072aed86963bac77c3ac