[#260] Use namespace as domain when resolve bucket

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

api/router_mock_test.go

@@ -18,6 +18,12 @@ func (c *centerMock) Authenticate(*http.Request) (*middleware.Box, error) {
 	return &middleware.Box{}, nil
 }
 
+type requestSettingsMock struct{}
+
+func (r *requestSettingsMock) NamespaceHeader() string {
+	return "X-Frostfs-Namespace"
+}
+
 type handlerMock struct {
 	t *testing.T
 }