Xsession creation of XDG user directories does not honor system umask policy

Issue

• A graphical login is initiated by the X display manager (e.g. gdm) for a user by running a generic Xsession which eventually executes a concrete session (e.g. gnome-session) in the context of the user's login shell. The umask of the login shell can be managed by script (e.g. /etc/profile) to establish a system policy for user created files. However, Xsession sources xdg-user-dirs.sh before this umask policy is set which results in the creation of XDG user directories that don't honor it.