Fix: Add arbitrary wait period for kernel streaming test

Once the trace has been destroy, there is a race condition between
reading the trace and the trace being completely written on disk.

We don't have anyway of telling if the streamed trace has been completed
so we have to add an arbitrary wait period so the test can successfully
parse and validate the trace.

I never hit that problem until this morning with my Linux 3.6.0 kernel.
Maybe related or not, still the trace can occur on slower systems.

Signed-off-by: David Goulet <dgoulet@efficios.com>