slapos.recipe:wrapper: add py3 support for pidfile and private-tmpfs

These two options were unusable for software releases using python3.

This also adds test coverage for the recipe.
Status Job ID Name Coverage
  External
running ERP5.StandaloneDeploymentScriptTest-Debian.Buster.Master

20594:31:50

running SlapOS.Eggs.UnitTest-Jerome.Python2

20594:31:23

running SlapOS.Eggs.UnitTest-Master.Python2

20594:31:48

running SlapOS.SlapRunner.ResilienceTest-Master

20594:31:37

running SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

20594:31:59

running SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

20594:31:23