This is necessary for calculating the total storage
capacity from object layer. This value is also needed for
browser UI.
Buckets used to carry this information, this patch
deprecates this feature.
It is the bucket and volumes which needs to have this
value rather than the DiskInfo API itself. Eventually
this can be extended to show disk usage per
Buckets/Volumes whenever we have that functionality.
For now since buckets/volumes are thinly provisioned
this is the right approach.
