Adding mount policy check without PolicyKit

[David Zeuthen]

Martin Pitt wrote:
> Hi,
> 
> When building hal without policykit, the mount backend solely relies
> on volume.ignore=true. This seems a bit fragile to me, and since we
> want to integrate mounting of fixed hard disks into the desktop, too
> [1], I added a policy check to the backend.
> 
> Do you consider adding this upstream, too?

Certainly, I've committed this. Thanks.

      David