Fixed vpnaas agent for RedHat systems

The package vpnaas package was not installed by default for RedHat
systems, and the service had the incorrect name. This patch
installs the package and sets the correct service name.

Backport to stable/havana

Change-Id: Id54dfbcb918d7d9ba110eb238858162c5cc0380e
Merge "Fixed vpnaas agent for RedHat systems"