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

18269:45:12

running SlapOS.Eggs.UnitTest-Jerome.Python2

18269:44:45

running SlapOS.Eggs.UnitTest-Master.Python2

18269:45:10

running SlapOS.SlapRunner.ResilienceTest-Master

18269:44:59

running SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

18269:45:22

running SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

18269:44:45