At the moment, everytime you want to test ILL you have to either add a patron category ILLIBS or you have to update the koha-conf.xml to use the existing IL category type from the sample data. As we have CPL as a sample branch in the koha-conf.xml, I think it would make sense to also change the patron category to match our sample data.
This should already be fixed by bug 21548 *** This bug has been marked as a duplicate of bug 21548 ***