update $WAYLAND_DISPLAY and $DISPLAY post login

The $WAYLAND_DISPLAY and $DISPLAY are prone to change between `greetd`'s
initialization and the user's login. Therefore, update these environment
variables so systemd services and/or d-bus services use the correct
values post login.

data/start-cosmic

@@ -40,7 +40,13 @@ export DCONF_PROFILE=cosmic
 
 if command -v dbus-update-activation-environment >/dev/null; then
     # set environment variables for new units started by user service manager
-    dbus-update-activation-environment --systemd XDG_SESSION_TYPE XDG_CURRENT_DESKTOP DCONF_PROFILE
+    dbus-update-activation-environment --systemd \
+        DCONF_PROFILE \
+        DISPLAY \
+        WAYLAND_DISPLAY \
+        XDG_CURRENT_DESKTOP \
+        XDG_SESSION_TYPE \
+        # EOF
 fi
 # Run cosmic-session
 if [[ -z "${DBUS_SESSION_BUS_ADDRESS}" ]]; then