bgpd: scope evpn specific path selection to type-2 routes

bgpd: scope evpn specific path selection to type-2 routes

For EVPN routes, there is specific logic in place for path selection
surrounding MAC Mobility.  For pure type-5 routes, if a route is
advertised with a MED, this is ignored since it ultimately falls inside
of the EVPN specific path selection logic, and ultimately selects the
lower IP address.  This change ensures only type-2 routes fall into the
EVPN BGP path selection.

Signed-off-by: Neal Shrader <neal@digitalocean.com>