Draft: monitor/udisks2: Only count devices on seats we're running on
If gvfs is run as a user unit, we take care of all the sessions of that user and the seats they're on. If gvfs is run in a session scope, we take care of the seat this session is on, if any. If we detect no multi-seat support on the system, we assume all storage devices are ours.
Edited by Arseny