Xi: Ensure DeviceChanged is emitted after grabs are deactivated

Xi: Ensure DeviceChanged is emitted after grabs are deactivated

When a grab on a slave device is deactivated, the master device must
be checked, just in case there were events from other devices while
the slave device was stolen away by the passive grab. This may
introduce misbehaviors on mismatching valuators and device features
later on UpdateDeviceState().

Signed-off-by: Carlos Garnacho <carlosg@gnome.org>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>