Fixed neutron-vpn-agent service conflict with neutron-l3-agent service & added some mandatory sysctl parameters

- Network configuration (such as IP addresses, default gateway...) shall now be set up beforehand. It is not done by the base class anymore. We now simply use the IPs from configured interfaces.
- Reworked +Fixed some things in Neutron networking services too.

Added/Fixed Neutron services for server/router/client. The router works well even when we only have one NIC