compositor-x11: Flush xcb connection from x11_output_destroy()

Current code flushes the connection when it receives
a delete window request. This means that a destroyed
window will remain available when X11 output gets
removed differently (ie, from a testing module).

Signed-off-by: Armin Krezović <krezovic.armin@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
1 file changed