[Libvirt-cim] [PATCH 0 of 2] SD: check client given object path

[Heidi Eckhart]

To enable the check of the client's given object path for Devices, the first tiny reorg in the Device provider is necessary. Thereby the get_device() function is made available for external use.
The second patch fixes the missing check of the client's given object in SystemDevice provider - for both directions.