gdbus: Fix memleak using g_task_propagate_pointer
gdbus: Fix memleak using g_task_propagate_pointer

https://bugzilla.gnome.org/show_bug.cgi?id=778993

frida/vala,frida/vala,GNOME/vala,frida/vala,GNOME/vala,frida/vala,frida/vala,GNOME/vala,GNOME/vala