In the normal course of script execution, clone_repo.sh routinely logs
the following error message:
error: pathspec 'xxx' did not match any file(s) known to git
This error can be safely ignored, as the script moves on to checking out
master instead. But it can be (and has been) mistakenly interpreted as
the reason why the script fails.
This change avoids logging the error message and logs a clearer
explanation instead.
Change-Id: Iaaaed7b0ea343bd81b8ad898654658545942a3d0
885330b8e7