slapos/collect: enable disk usage

See merge request !311
4 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS-Master.UnitTest-Master

01:07:20

passed SlapOS.Eggs.UnitTest-Master.Python2

00:26:50

passed SlapOS.Eggs.UnitTest-Master.Python3

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:09