fixup! EggTestSuite: support --log_directory

this was not working either when testnode does not pass log_directory
4 jobs for arnau in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

02:02:30

failed ERP5.UnitTest-Master

passed SlapOS.Eggs.UnitTest-Master.Python2

passed SlapOS.Eggs.UnitTest-Master.Python3