fix accessibility on XCB when running as root

fix accessibility on XCB when running as root

Origin: https://codereview.qt-project.org/c/qt/qtbase/+/205196
Bug: https://bugs.debian.org/1033995
Last-Update: 2023-04-12

Accessibility actually works when running applications as root, but we
would never properly connect, since the enabledChanged signal would be
emitted from the constructor in this case. So after connecting the
signal, check the value by hand to make sure not to miss the
notification.

Only applications running as root would be affected, because all other
applications would go through the asynchronous pattern of getting the
bus address from dbus instead.

Gbp-Pq: Name a11y_root.diff