Modify test to avoid race condition.

There is a possible race if a timer is set to trigger at nearly the same
time as it is set. Since nobody uses the timers like this, modify the test
so this doesn't happen. The race that this can provoke has been fixed in
aosp.

Bug: 19423618
Change-Id: I21084c99da5ae46f404936d673dae6bad7c82caa