Move metering_secret to publisher section

In Icehouse, metering_secret has been moved to [publisher]:
http://git.io/11NwNw

Change-Id: I96c70781902e927c0295af78c93b400d7b4684bb
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge "Move metering_secret to publisher section"