migrate to upstream libcompose in one and a half go

vendor/github.com/docker/libnetwork/drivers_freebsd.go

@@ -1,19 +1,13 @@
 package libnetwork
 
 import (
-	"github.com/docker/libnetwork/driverapi"
 	"github.com/docker/libnetwork/drivers/null"
 	"github.com/docker/libnetwork/drivers/remote"
 )
 
-func initDrivers(dc driverapi.DriverCallback) error {
-	for _, fn := range [](func(driverapi.DriverCallback) error){
-		null.Init,
-		remote.Init,
-	} {
-		if err := fn(dc); err != nil {
-			return err
-		}
+func getInitializers() []initializer {
+	return []initializer{
+		{null.Init, "null"},
+		{remote.Init, "remote"},
 	}
-	return nil
 }