sync periodic_task fix from incubator

Set the value of time the periodic task was last run to a multiple of the
spacing value rather than the actual last time run. This ensures tasks runs
regularly but avoids synchronizing that interval with other nodes.

This patch also removes the coalescing of tasks which are _nearby_ (0.2
seconds away).

4dbd3aa Make periodic tasks run on regular spacing interval
21249f1 Fix parenthesis typo misunderstanding in periodic_task

Change-Id: I8873545578f104fd204fbc25493350128b2bc8d4
Merge "sync periodic_task fix from incubator"