smoketest: T3871: enable allow-unsupported-nics for vpp config migration test

eth4 in the vpp migration test config is not a validated VPP NIC, so
vyos-configtest failed on commit with "NIC used by eth4 is not
validated for VPP". Add allow-unsupported-nics to the input config
and its matching assert file.

Author: c-po

smoketest/configs/assert/vpp

@@ -39,6 +39,7 @@ set interfaces vpp loopback vpplo12 description 'Loop12'
 set interfaces vpp vxlan vppvxlan10 remote '192.0.2.2'
 set interfaces vpp vxlan vppvxlan10 source-address '192.0.2.1'
 set interfaces vpp vxlan vppvxlan10 vni '10'
+set vpp settings allow-unsupported-nics
 set vpp settings interface eth1
 set vpp settings interface eth2
 set vpp settings interface eth3

smoketest/configs/vpp

@@ -111,6 +111,7 @@ vpp {
         }
     }
     settings {
+        allow-unsupported-nics
         interface eth1 {
             driver "dpdk"
         }