Don't reset PYTHONPATH

With slapos!862 we no longer need this

See merge request !270
7 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS-Master.UnitTest-Master

01:29:39

passed SlapOS.Eggs.UnitTest-Master.Python2

00:08:37

passed SlapOS.Eggs.UnitTest-Master.Python3

00:13:24

passed SlapOS.Eggs.UnitTest-Master.Python2

00:43:22

passed SlapOS.Eggs.UnitTest-Master.Python2

00:24:02

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:16

passed SlapOS.Eggs.UnitTest-Master.Python3

00:29:40