content: support filters on local.store#Walk()

While Walk() has been taking filter strings, it was not using the parameter.
This change actually makes the filtering work.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

metadata/adaptors.go

@@ -90,25 +90,6 @@ func adaptContainer(o interface{}) filters.Adaptor {
 	})
 }
 
-func adaptContentInfo(info content.Info) filters.Adaptor {
-	return filters.AdapterFunc(func(fieldpath []string) (string, bool) {
-		if len(fieldpath) == 0 {
-			return "", false
-		}
-
-		switch fieldpath[0] {
-		case "digest":
-			return info.Digest.String(), true
-		case "size":
-			// TODO: support size based filtering
-		case "labels":
-			return checkMap(fieldpath[1:], info.Labels)
-		}
-
-		return "", false
-	})
-}
-
 func adaptContentStatus(status content.Status) filters.Adaptor {
 	return filters.AdapterFunc(func(fieldpath []string) (string, bool) {
 		if len(fieldpath) == 0 {