Move service to execution package

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

execution/executors/oci/oci.go

@@ -10,16 +10,10 @@ import (
 
 	"github.com/crosbymichael/go-runc"
 	"github.com/docker/containerd/execution"
-	"github.com/docker/containerd/executors"
 )
 
 var ErrRootEmpty = errors.New("oci: runtime root cannot be an empty string")
 
-func init() {
-	executors.Register("oci", New)
-	executors.Register("runc", New)
-}
-
 func New(root string) *OCIRuntime {
 	return &OCIRuntime{
 		root: root,