neutron-metering-agent service name is wrong

In Ubuntu the neutron-metering-agent package and Upstart service are named
neutron-plugin-metering-agent. In Debian they are named
neutron-metering-agent.

Partial-Bug: #1284179
(cherry picked from commit 57e16648629b8c541e094b848cecac53137949c4)

Change-Id: I76b56886a4d239b279731dc1e85c17a7f380aa76
Merge "neutron-metering-agent service name is wrong" into stable/havana