Don't allow swift-recon cron job to send mail

The cron job is periodically sending out emails. They are going
to root's mailbox and would likely be left unread.

swift-recon-cron logs its activities so the emails are not
needed.

Change-Id: Idf66b59b883e13b2f4aa4fcfd575adc89e770d98
Closes-Bug: 1354262
Merge "Don't allow swift-recon cron job to send mail"