Queries this's backend for a property of name prop_name.
The call is finished by get_backend_property.end from the callback.
| this |
an Client |
| prop_name |
property name, whose value to retrieve; cannot be null |
| cancellable |
a Cancellable; can be null |
| callback |
callback to call when a result is ready |
| user_data |
user data for the |