add delete-marker proactively in DeleteObject() (#13795)

single object delete was not working properly
on a bucket when versioning was suspended,
current version 'null' object was never removed.

added unit tests to cover the behavior

fixes #13783

cmd/xl-storage.go

@@ -954,11 +954,11 @@ func (s *xlStorage) DeleteVersion(ctx context.Context, volume, path string, fi F
 		if err != errFileNotFound {
 			return err
 		}
+		metaDataPoolPut(buf) // Never used, return it
 		if fi.Deleted && forceDelMarker {
 			// Create a new xl.meta with a delete marker in it
 			return s.WriteMetadata(ctx, volume, path, fi)
 		}
-		metaDataPoolPut(buf) // Never used, return it
 
 		buf, err = s.ReadAll(ctx, volume, pathJoin(path, xlStorageFormatFileV1))
 		if err != nil {
@@ -1016,6 +1016,7 @@ func (s *xlStorage) DeleteVersion(ctx context.Context, volume, path string, fi F
 			}
 		}
 	}
+
 	if !lastVersion {
 		buf, err = xlMeta.AppendTo(metaDataPoolGet())
 		defer metaDataPoolPut(buf)