Created attachment 212369 [details] [review]
Remove refcounting increment on device proxy when using it.

In function nm_device_new, device_proxy refcount was incremented.
device_proxy is created in function device_proxy_new_cb() by g_dbus_proxy_new_for_bus_finish call. After this call, refcount = 1.

When in device_proxy_new_cb(), nm_device_new() is called, device_proxy refcount=2.

So when nm_device_free() is called, device_proxy refcount=1 and such is not deleted.

The bug is not critical and doesn't make gupnp crash because device_proxy is not set to NULL after calling g_object_unref in nm_device_free.

The side effect is that as the context is not destroyed, the signal handler on this proxy still exist.
The signal has been set in use_new_device() function. 
g_signal_connect (nm_device->proxy,
                  "g-signal",
                  G_CALLBACK (on_device_signal),
                  nm_device);

If nm_device->proxy was set to NULL in nm_device_free(), a crash will/could occurs.

The side effect is that the callback is called for a device proxy that should be destroyed.