A few more cleanups
A few more cleanups

    - exit 0 is implicit when there are no errors
    - Ensure $ARC_DIR is created via mkdir -p
    - Make usage stdout redirect to stderr where usage info should go

sue445/jenkins-backup-script,yonexyonex/jenkins-backup-script,orafapires/jenkins-backup-script,yonexyonex/jenkins-backup-script,sue445/jenkins-backup-script,jonnyro/jenkins-backup-script,jonnyro/jenkins-backup-script,orafapires/jenkins-backup-script