Provide initial postinst script for ngcp-mediaproxy-ng-daemon

As requested by Richard (to address the "the post-install script
for mediaproxy-daemon is not correct, it should not start up in
a pro when on the standby node" issue)

From: Michael Prokop <mprokop@sipwise.com>

debian/ngcp-mediaproxy-ng-daemon.postinst

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+set -e
+
+#DEBHELPER#
+