[#1667] shard: Drop shard pool

After adding an ops limiter, shard's `put` pool is redundant.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/engine/control_test.go

@@ -245,7 +245,6 @@ func TestReload(t *testing.T) {
 
 		// no new paths => no new shards
 		require.Equal(t, shardNum, len(e.shards))
-		require.Equal(t, shardNum, len(e.shardPools))
 
 		newMeta := filepath.Join(addPath, fmt.Sprintf("%d.metabase", shardNum))
 
@@ -257,7 +256,6 @@ func TestReload(t *testing.T) {
 		require.NoError(t, e.Reload(context.Background(), rcfg))
 
 		require.Equal(t, shardNum+1, len(e.shards))
-		require.Equal(t, shardNum+1, len(e.shardPools))
 
 		require.NoError(t, e.Close(context.Background()))
 	})
@@ -277,7 +275,6 @@ func TestReload(t *testing.T) {
 
 		// removed one
 		require.Equal(t, shardNum-1, len(e.shards))
-		require.Equal(t, shardNum-1, len(e.shardPools))
 
 		require.NoError(t, e.Close(context.Background()))
 	})
@@ -311,7 +308,6 @@ func engineWithShards(t *testing.T, path string, num int) (*StorageEngine, []str
 	}
 
 	require.Equal(t, num, len(e.shards))
-	require.Equal(t, num, len(e.shardPools))
 
 	return e, currShards
 }