Debian: fix package and service names

In previous commits, Neutron Metering and VPNaaS agents services and
packages names have been modified to support Ubuntu, in breaking Debian
support.
This patch aims to fix it.

Change-Id: Iff9f8a925bca8534fe6672c3ab84513aa0416cd5
Partial-Bug: #1284179
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>