s3: recursively iterate all sub folders

fix https://github.com/chrislusf/seaweedfs/issues/1656

weed/s3api/s3api_objects_list_handlers.go

@@ -197,11 +197,12 @@ func (s3a *S3ApiServer) doListFilerEntries(client filer_pb.SeaweedFilerClient, d
 		sepIndex := strings.Index(marker, "/")
 		subDir, subMarker := marker[0:sepIndex], marker[sepIndex+1:]
 		// println("doListFilerEntries dir", dir+"/"+subDir, "subMarker", subMarker, "maxKeys", maxKeys)
-		subCounter, _, subNextMarker, subErr := s3a.doListFilerEntries(client, dir+"/"+subDir, "", maxKeys, subMarker, delimiter, eachEntryFn)
+		subCounter, subIsTruncated, subNextMarker, subErr := s3a.doListFilerEntries(client, dir+"/"+subDir, "", maxKeys, subMarker, delimiter, eachEntryFn)
 		if subErr != nil {
 			err = subErr
 			return
 		}
+		isTruncated = isTruncated || subIsTruncated
 		maxKeys -= subCounter
 		nextMarker = subDir + "/" + subNextMarker
 		counter += subCounter