*: appc/cni -> containernetworking/cni

The project has been moved so internally we simply rename everything.
Consumers are recommended to update their vendored version of cni.

pkg/invoke/exec.go

@@ -21,7 +21,7 @@ import (
 	"os"
 	"os/exec"
 
-	"github.com/appc/cni/pkg/types"
+	"github.com/containernetworking/cni/pkg/types"
 )
 
 func pluginErr(err error, output []byte) error {