[#949] metabase: fix shard.UpdateID()

metabase.Open() now reports metabase mode metric. shard.UpdateID()
needs to read shard ID from metabase => needs to open metabase.
It caused reporting 'shard undefined' metrics. To avoid reporting
wrong metrics metabase.GetShardID() was added which also opens
metabase and does not report metrics.

Signed-off-by: Ekaterina Lebedeva <ekaterina.lebedeva@yadro.com>

pkg/local_object_storage/metabase/version_test.go

@@ -58,9 +58,7 @@ func TestVersion(t *testing.T) {
 	})
 	t.Run("old data", func(t *testing.T) {
 		db := newDB(t)
-		require.NoError(t, db.Open(context.Background(), mode.ReadWrite))
-		require.NoError(t, db.WriteShardID([]byte{1, 2, 3, 4}))
-		require.NoError(t, db.Close())
+		require.NoError(t, db.SetShardID([]byte{1, 2, 3, 4}, mode.ReadWrite))
 
 		require.NoError(t, db.Open(context.Background(), mode.ReadWrite))
 		require.NoError(t, db.Init())