Make stop_timers() method public

This is needed to fix Heat bug 1315044.

Change-Id: I0f92235beaa1bfd548688c9b0803f9931bc9dac8
(cherry picked from commit 5a1a01667eb8c08999c0e31ef281f7b98a0c9cbc)
Merge "Make stop_timers() method public" into stable/icehouse