ddns-scripts: only start via hotplug not via boot

Hotplug script will start service for each interface.
To prevent duplicates and in general must not start on boot.

Signed-off-by: Christian Schoenebeck <christian.schoenebeck@gmail.com>

net/ddns-scripts/files/etc/init.d/ddns

@@ -1,6 +1,10 @@
 #!/bin/sh /etc/rc.common
 START=95
 
+boot() {
+	return 0
+}
+
 start() {
 	. /usr/lib/ddns/dynamic_dns_functions.sh
 	start_daemon_for_all_ddns_sections