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

24022:17:25

running SlapOS.Eggs.UnitTest-Jerome.Python2

24022:16:57

running SlapOS.Eggs.UnitTest-Master.Python2

24022:17:22

running SlapOS.SlapRunner.ResilienceTest-Master

24022:17:11

running SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

24022:17:34

running SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

24022:16:57