Merge pull request opencontainers#85 from q384566678/test-layers

config.go:Drop local rootfs.type validation

Author: xiekeyang

image/config.go

@@ -53,10 +53,7 @@ func findConfig(w walker, d *descriptor) (*config, error) {
 		if err := json.Unmarshal(buf, &c); err != nil {
 			return err
 		}
-		// check if the rootfs type is 'layers'
-		if c.RootFS.Type != "layers" {
-			return fmt.Errorf("%q is an unknown rootfs type, MUST be 'layers'", c.RootFS.Type)
-		}
+
 		return errEOW
 	}); err {
 	case nil: