Use Zuul to send email for periodic jobs

Stop having Jenkins send the email reports and use the "new" smtp
reporter in Zuul to send them.  This will consolodate the emails
(currently one per job) into a smaller number of summary email
reports, which will be much more useful to the stable maint teams.

They will also not include useless truncated console logs, but
will contain links to the log server.

This is a preliminary step to eliminate the periodic job definitions
altogether.

Change-Id: If637e0f4491ddbbb4d4e5806b0f999e21d8aa10f
Merge "Use Zuul to send email for periodic jobs"