pkg,plugins: update for Result struct Interface index changes

It's a pointer now, so we need to use the helper function to set
the field and also test for nil before accessing it.

plugins/meta/portmap/portmap_integ_test.go

@@ -134,7 +134,8 @@ var _ = Describe("portmap integration tests", func() {
 		var contIP net.IP
 
 		for _, ip := range result.IPs {
-			if result.Interfaces[ip.Interface].Sandbox == "" {
+			intfIndex := *ip.Interface
+			if result.Interfaces[intfIndex].Sandbox == "" {
 				continue
 			}
 			contIP = ip.Address.IP