Comment 3 for bug 1724147

Reviewed: https://review.openstack.org/515674
Committed: https://git.openstack.org/cgit/openstack/mistral/commit/?id=fd979d95d613e40be228695c0471c73cf9a5e3f4
Submitter: Zuul
Branch: stable/pike

commit fd979d95d613e40be228695c0471c73cf9a5e3f4
Author: Renat Akhmerov <email address hidden>
Date: Tue Oct 17 14:09:36 2017 +0700

    Add a config option to disable cron triggers

    * Cron triggers (implemented in periodic.py) are always enabled
      although in many installations they are not needed. When they
      are enabled they consume resoruces (keep polling DB etc.).
      This patch add the config option "enabled" under "cron_trigger"
      group that can be used to disable the entire subsystem.
    * Wiped out "disable_cron_trigger_thread" pecan app config variable
      that was use to disable cron triggers in unit tests in favor of
      the new config option
    * Other minor style changes

    Closes-bug: #1724147
    Change-Id: I79b9ccb2f4286b3ea8696b7cd65472c8a49937bf
    (cherry picked from commit 6efe094012de5458ac66bbaf93a38005b8e69c2d)