CTabFolder would signal a D&D timeout because gdk_event_get() was not
receiving anything in Wayland. Using gdk_window_get_device_position() we
can get the current mouse status to see if it was a release event to
leave the timeout loop correctly.

Change-Id: If6aa70d945f116dec6b5613835bdfd7c03b89c4d
Signed-off-by: Ian Pun <ipun@redhat.com>