fff-nodewatcher: only run uci-defaults once

If /etc/config/nodewatcher already exists, a proper uci-defaults
script should not overwrite it. Since this package is the owner
of the config file, this change won't change anything for the
current firmware, but will allow to use this as a package, too.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Reviewed-by: Robert Langhammer <rlanghammer@web.de>

src/packages/fff/fff-nodewatcher/files/etc/uci-defaults/93-fff-nodewatcher

@@ -1,3 +1,5 @@
+[ -s /etc/config/nodewatcher ] && exit 0
+
 touch /etc/config/nodewatcher
 
 uci batch >/dev/null <<EOF