Bug 1230: Don't run VTN Coordinator test that may fail under heavy load.

Some VTN Coordinator tests may fail if the build host is under heavy load,
especially tests that require accuracy of system timer.
This patch eliminates those tests.

This patch also merges commit 153e6a34bd0272436e3ee7c08b404841d6061c5d
that fixes trivial issue on VTN Coordinator UT.

Change-Id: I9bc76e7256799a415003a00698e8d9c275d7f7d6
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>
(cherry picked from commit 444f3aef7b6ddbac9d54d7a00576b660511342e2)