desktop-shell: add option to not use locking

Add an option to the desktop-shell ini file that defines whether screen
locking is used or not.

Useful for testing screensaver interactions without a lock surface.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
diff --git a/wayland-desktop-shell.ini b/wayland-desktop-shell.ini
index 8c7c1f9..3a86935 100644
--- a/wayland-desktop-shell.ini
+++ b/wayland-desktop-shell.ini
@@ -1,6 +1,7 @@
 [wayland-desktop-shell]
 background-image=/usr/share/backgrounds/gnome/Aqua.jpg
 panel-color=0x90ff0000
+locking=true
 
 [launcher]
 icon=/usr/share/icons/gnome/24x24/apps/utilities-terminal.png