Load Balancer: Use FIB 2.0

Load Balancer: Use FIB 2.0

This patch fixes load balancer, which was not working
since FIB 2.0.

Two FIB DPO types are defined:
- One for IPv4 GRE
- One for IPv6 GRE

When an AS is created, the plugin automatically uses
the result from the FIB in order to transmit the packet.
Therefore, the packet does not need to visit ip-lookup twice.

The 'bypass' command was removed, as it is now done
automatically using this process.

Change-Id: Ib505ba31bfc67897eaff752821087821c360360a
Signed-off-by: Pierre Pfister <ppfister@cisco.com>