slapos_jio: Support list of elements expressed with oneOf

See merge request !248
5 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS-Master.UnitTest-Master

01:45:24

passed SlapOS.Eggs.UnitTest-Master.Python2

00:25:48

passed SlapOS.Eggs.UnitTest-Master.Python3

00:17:49

passed SlapOS.Eggs.UnitTest-Master.Python2

00:16:01

passed SlapOS.Eggs.UnitTest-Master.Python3

00:30:08