Turn periodic tasks off in all unit tests

We shouldn't rely on periodic tasks to randomly run in unit tests,
instead if we need them to run we should explicitly call them out.

Change-Id: I35850c47288e50d3146771dc7a9a54d62e36c3cf
Related-Bug: 1311778
(cherry picked from commit f3f07f4401ff8be25598493c088e4e100b387fe4)
Merge "Turn periodic tasks off in all unit tests" into stable/icehouse