xwayland: Fixed timeout during start-up

The weston-start script for xwayland overrides the module loading of the
notify library. Without notify, Weston doesn't report a successful start
back so systemd. As a result, systemd stops Weston after hitting the
timeout period.

Without the module loading directive in the start script, xwayland needs
to be activated in the weston.ini.

(cherry picked from commit 510cc193)

recipes-graphics/wayland/weston/xwayland.weston-start

+#!/bin/sh
+
+if type Xwayland >/dev/null 2>/dev/null; then
+    mkdir -p /tmp/.X11-unix
+fi