shell/caucase.sh: Split file-or-folder detection from updateCACertificate.

So it can be reused elsewhere.
4 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Master.Python2

00:15:19

passed SlapOS.Eggs.UnitTest-Master.Python3

00:09:57

passed SlapOS.Eggs.UnitTest-Master.Python2

00:10:50

passed SlapOS.Eggs.UnitTest-Master.Python3

00:26:51