api: status: include empty entry for stores with ns-only privs

api: status: include empty entry for stores with ns-only privs

I.e., for those that only got permissions on a sub namespace and
those that onlöy got BACKUP_READ, as both they could just list and
count themselves too after all, so not exactly secret info.

The UI needs some adaptions to cope with gc-stats and usage being
optional, will be done in a next commit.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>