[#1770] engine: Support configuration reload

Currently, it only supports changing the compound of the shards.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/local_object_storage/engine/shards_test.go

@@ -0,0 +1,46 @@
+package engine
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRemoveShard(t *testing.T) {
+	const numOfShards = 6
+
+	e := testNewEngineWithShardNum(t, numOfShards)
+	t.Cleanup(func() {
+		e.Close()
+		os.RemoveAll(t.Name())
+	})
+
+	require.Equal(t, numOfShards, len(e.shardPools))
+	require.Equal(t, numOfShards, len(e.shards))
+
+	removedNum := numOfShards / 2
+
+	mSh := make(map[string]bool, numOfShards)
+	for i, sh := range e.DumpInfo().Shards {
+		if i == removedNum {
+			break
+		}
+
+		mSh[sh.ID.String()] = true
+	}
+
+	for id, remove := range mSh {
+		if remove {
+			require.NoError(t, e.removeShards(id))
+		}
+	}
+
+	require.Equal(t, numOfShards-removedNum, len(e.shardPools))
+	require.Equal(t, numOfShards-removedNum, len(e.shards))
+
+	for id, removed := range mSh {
+		_, ok := e.shards[id]
+		require.True(t, ok != removed)
+	}
+}