tests: aonc: skip counter stopping

Leave the aon counter in running state after the test.

Arduino 101 loader assumes the counter is running.
Stopping the counter will cause the next app to
not start without a hard reset or power cycle.

Jira: ZEP-961

Change-Id: Ia88f0c642b1df8dc5e2b1ee6c55ff0618b6127d0
Signed-off-by: Baohong Liu <baohong.liu@intel.com>