allow preserving legacyXLv1 with inline data format (#11951)

current master breaks this important requirement
we need to preserve legacyXLv1 format, this is simply
ignored and overwritten causing a myriad of issues
by leaving stale files on the namespace etc.

for now lets still use the two-phase approach of
writing to `tmp` and then renaming the content to
the actual namespace.

cmd/erasure-metadata.go

@@ -279,6 +279,37 @@ func pickValidFileInfo(ctx context.Context, metaArr []FileInfo, modTime time.Tim
 	return findFileInfoInQuorum(ctx, metaArr, modTime, quorum)
 }
 
+// Rename metadata content to destination location for each disk concurrently.
+func renameFileInfo(ctx context.Context, disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, quorum int) ([]StorageAPI, error) {
+	ignoredErr := []error{errFileNotFound}
+
+	g := errgroup.WithNErrs(len(disks))
+
+	// Rename file on all underlying storage disks.
+	for index := range disks {
+		index := index
+		g.Go(func() error {
+			if disks[index] == nil {
+				return errDiskNotFound
+			}
+			if err := disks[index].RenameData(ctx, srcBucket, srcEntry, "", dstBucket, dstEntry); err != nil {
+				if !IsErrIgnored(err, ignoredErr...) {
+					return err
+				}
+			}
+			return nil
+		}, index)
+	}
+
+	// Wait for all renames to finish.
+	errs := g.Wait()
+
+	// We can safely allow RenameData errors up to len(er.getDisks()) - writeQuorum
+	// otherwise return failure. Cleanup successful renames.
+	err := reduceWriteQuorumErrs(ctx, errs, objectOpIgnoredErrs, quorum)
+	return evalDisks(disks, errs), err
+}
+
 // writeUniqueFileInfo - writes unique `xl.meta` content for each disk concurrently.
 func writeUniqueFileInfo(ctx context.Context, disks []StorageAPI, bucket, prefix string, files []FileInfo, quorum int) ([]StorageAPI, error) {
 	g := errgroup.WithNErrs(len(disks))