ffs-set-segment: check uci instead of pidfile

In gluon master, fastd doesn't seem to create a pid file any more. Since
the only purpose was to see if a mesh-VPN connection is establishe, we
can simply check uci instead.

ffs-set-segment/files/usr/sbin/ffs-set-segment

@@ -4,7 +4,7 @@ if [ $(ps | grep -c "$ME") -gt 4 ]; then
   logger -s -t $ME "started twice"
   exit 1
 fi
-if [ ! -d "/proc/$(cat /var/run/fastd.mesh_vpn.pid)" ]; then
+if [ "$(uci get fastd.mesh_vpn.enabled)" = "0" ]; then
   logger -t $ME "fastd not running"
   exit 0
 fi