Fix for issue #2765 relative to unstable test

Fix for issue #2765 relative to unstable trafficshaping test procedure

Motivation:
The test procedure is unstable due to not enough precise timestamping during the check.

Modifications:
Reducing the test cases and cibling "stable" test ("timestamp-able") bring more stability to the tests.

Result:
Tests for TrafficShapingHandler seem more stable (whatever using JVM 6, 7 or 8).
Same version as in 4.0, 4.1 and Master.