improve timing sensitive test to avoid failed tests on travis
improve timing sensitive test to avoid failed tests on travis

mapproxy/mapproxy,vrsource/mapproxy,camptocamp/mapproxy,olt/mapproxy,drnextgis/mapproxy,drnextgis/mapproxy,mapproxy/mapproxy,olt/mapproxy,vrsource/mapproxy,camptocamp/mapproxy