weston-init: support system's configuration file

Look for OPTARGS variable in /etc/default/weston
and set it as weston's service default options.

This can be used to force system's supported backend.

Change-Id: I0562c9326df5b46226093199873ef58d77aeae75
(From OE-Core rev: 8ffcdcc53bac64c62478fbb72d817c842dde8b28)

Signed-off-by: Philippe Coval <philippe.coval@open.eurogiciel.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-graphics/wayland/weston-init/init

@@ -8,6 +8,10 @@
 # Default-Stop:      0 1 6
 ### END INIT INFO
 
+if test -e /etc/default/weston ; then
+        . /etc/default/weston
+fi
+
 killproc() {
         pid=`/bin/pidof $1`
         [ "$pid" != "" ] && kill $pid
@@ -34,7 +38,7 @@ case "$1" in
                 chmod 0700 $XDG_RUNTIME_DIR
         fi
 
-        openvt -s weston
+        openvt -s weston -- $OPTARGS
   ;;
 
   stop)