This fixes an issue where, upon the first call into
weston_wm_window_read_properties after the hints->decorations
property had changed, the old value for this property was read in
weston_wm_window_read_properties
XWayland: When maximized, don't draw window decorations for windows that draw their own

This patch fixes an issue where window decorations were drawn for
fullscreen XWayland applications that draw their own window decorations
(eg. Google Chrome/Chromium)