Creating workitems for qt5 integrations takes a long time

When scheduling a status check from Webui, qt5 integrations might take up to 10-15 minutes until the workitems appear on the webui. 

The performance regression might be caused by commit f0e982cffa9627c158de1ef0e1cd7e0f35c9b89e which causes the repository manager to calculate sha1s for all workitem configs unconditionally despite the custom template is not set (contrary to the commit message of the previously mentioned patch).

This is a bug in workitemfactory that should be fixed.