gtkwindow: Clean up the code for an optimization

gtkwindow: Clean up the code for an optimization

It's hard to figure out what the "expected_reply" means except under
close examination -- it's actually talking about whether this was a
reply to a ConfigureRequest or not. The inversion in the check doesn't
help either.

Make the code cleaner by moving it above the freeze/thaw case, and
making the check more explicit and without a confusing variable. If we
haven't sent any ConfigureRequests out, then it must be a gratuitous
ConfigureNotify.