NEWT X11Window didn't gather inset at window creation (properly)
retrieves the insets via XGetWindowProperty on _NET_FRAME_EXTENTS.
Right after window creation this method fails as the WM did not yet
provide the information as the window has not yet been mapped.
Implementation needs to retry for a certain amount of time (250ms)
and maximum number of attempts (96 XEvent).
This issue surfaced while validating fix for Bug 1393,
testing TestDisplayLifecycle02NEWT also on X11.