info: Don't depend on udisks2 client library

The official implementation of udisks2 service is only available on Linux. Since the client library is bundled with the service, it is not possible to install the client library on non-Linux systems without patching the build system of udisks2. In order to support non-Linux systems with their unofficial udisks2 service implementations, we should use GDBus directly instead of relying on the client library.

Fixes #606 (closed)