Add wrappers that check the MODE in /etc/nut/nut.conf to avoid starting the daemons if nut is not configured (Closes: #747863).

debian/local/upsd

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+# Include NUT nut.conf
+[ -r /etc/nut/nut.conf ] && . /etc/nut/nut.conf
+
+case "$MODE" in
+  standalone|netserver)
+    exec /lib/nut/upsd "$@"
+  ;;
+  none|netclient)
+    echo "upsd disabled, please adjust the configuration to your needs"
+    echo "Then set MODE to a suitable value in /etc/nut/nut.conf to enable it"
+    # exit success to avoid breaking the install process!
+    exit 0
+  ;;
+  *)
+    exit 1
+  ;;
+esac