kunit: tool: unit tests all check parser errors, standardize formatting a bit

Let's verify that the parser isn't reporting any errors for valid
inputs.

This change also
* does result.status checking on one line
* makes sure we consistently do it outside of the `with` block

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