[#948] metrics: Set actual value for shard_id after restart

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

pkg/local_object_storage/writecache/writecache.go

@@ -41,6 +41,7 @@ type Cache interface {
 	Init() error
 	Open(ctx context.Context, mode mode.Mode) error
 	Close() error
+	GetMetrics() Metrics
 }
 
 // MainStorage is the interface of the underlying storage of Cache implementations.