Add an option to print job id of submitted jobs on stdout

Add an option to print job id of submitted jobs on stdout

When submitting a job, the job id, prefixed by 'JobID: ', is output to
stderr. While this is easy to understand for humans, for scripting, it
is more convenient to have (additionally) the id on stdout (and only
the id). Add an option to provide this.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Thomas Thrainer <thomasth@google.com>