Merge pull request #2434 from crosbymichael/shimv2

Runtime v2 (shim API)

cmd/containerd/builtins_linux.go

@@ -19,7 +19,8 @@ package main
 import (
 	_ "github.com/containerd/aufs"
 	_ "github.com/containerd/containerd/metrics/cgroups"
-	_ "github.com/containerd/containerd/runtime/linux"
+	_ "github.com/containerd/containerd/runtime/v1/linux"
+	_ "github.com/containerd/containerd/runtime/v2"
 	_ "github.com/containerd/containerd/snapshots/native"
 	_ "github.com/containerd/containerd/snapshots/overlay"
 	_ "github.com/containerd/zfs"