udisks2: Change display name for crypto_unknown devices
The udisks id_type crypto_unknown is used for devices which are possibly encrypted. In udisks, this uncertainty is conveyed to the user by using the long name "Possibly encrypted", and the short name "Encrypted?". GVfs used to display all devices with id_usage == "crypto" as "Encrypted". This commit instead uses the string "Possibly Encrypted" if id_type == "crypto_unknown".