Bug 1453: Fixed unstable unit tests.

This patch fixes unit tests that expected severe accuracy of timer task
execution.

Change-Id: Id0c3b33e2518f3e37a4b4cb495c4c2bdb8c0e964
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>
(cherry picked from commit 2344fd41c00808bcb2e61216b55f74ff863350f2)