BE: Schedule the refresh interval from the finish time of the last run
Related: https://pagure.io/SSSD/sssd/issue/4012
Changes scheduling the periodical task so that the next run is started
relative to the previous run finish time, not start time to protect
against cases where the refresh would take too long and run practically
all the time.
Reviewed-by: Sumit Bose <sbose@redhat.com>
(cherry picked from commit 576f3691a2d22322b08fb55fe74899d2ea4975d6)
Reviewed-by: Sumit Bose <sbose@redhat.com>