[#413] Add stream reading

Signed-off-by: Denis Kirillov <denis@nspcc.ru>

internal/neofs/tree.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io"
 	"strconv"
 	"strings"
 
@@ -406,6 +407,14 @@ func (c *TreeClient) getParent(ctx context.Context, cnrID *cid.ID, treeID string
 		return 0, fmt.Errorf("failed to get sub tree: %w", err)
 	}
 
+	for {
+		if _, err = cli.Recv(); err == io.EOF {
+			break
+		} else if err != nil {
+			return 0, fmt.Errorf("failed to read out sub tree stream: %w", err)
+		}
+	}
+
 	return resp.GetBody().GetParentId(), nil
 }