kunit: tool: make unit test not print parsed testdata to stdout

Currently, if you run
$ ./tools/testing/kunit/kunit_tool_test.py
you'll see a lot of output from the parser as we feed it testdata.

This makes the output hard to read and fairly confusing, esp. since our
testdata includes example failures, which get printed out in red.

Silence that output so real failures are easier to see.

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>