nmigen_cfu: turn off trace in tests
nmigen_cfu: turn off trace in tests

Turn off tracing in test cases by default.

Signed-off-by: Alan Green <97e77871b5fcc4941bebceb4338c97c1fd149f8c@google.com>

google/CFU-Playground,google/CFU-Playground,google/CFU-Playground,google/CFU-Playground