Speed up per-commit test for nextgenv2 branch

Speed up per-commit test for nextgenv2 branch

Jenkins per-commit test need to be expedited as more experiments are
added into the nextgenv2 branch. This patch does the following:

thread test: change the length of test clip from 5 frames to 3 frames;
only test speed 1.
ArfFreq test: marked as "large".

The tests marked as "large" will be removed from per-commit test
(to nightly test).

Change-Id: I62b373c52b481dcd281e741ebf5098408a97ff4d