fixup! fixup! erp5.util.testnode: tell SR to clone in shared mode

checkRevision now returns a callable, return a do-nothing lambda when
the expected revision is already checked out
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Jerome.Python2

00:18:33

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:23:58