Fix the signal handling; you can't use this.connect('ActiveChanged')
to connect to a D-Bus signal after replacing the signal methods with
the lang.signals versions. Just leave it using the D-Bus signal names,
just like it uses the D-Bus method names.
Also, remove the "_" from "_screenSaverActive", to match what
AutomountManager checks for, and remove getActive(), since it's not
needed.
https://bugzilla.gnome.org/show_bug.cgi?id=654550