ffs-set-segment: don't bring down/up client

This might cause mesh-vpn to go missing from batctl if.

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

@@ -67,9 +67,8 @@ do
 done
 
 if [ "$CHANGED" = "1" ]; then
-  /sbin/ifdown client
   /etc/init.d/fastd restart
-  /sbin/ifup client
+  /sbin/ip addr flush dev br-client
   logger -t $ME "Set Segment: $GITSEG"
 else
   logger -t $ME "No changes"