Convert test suite to OUnit2 before running

This is needed since running an OUnit 1.x test suite using OUnit2 installed
does not return non-zero exit code even on failure or error.

Converting the suite at this point is desirable in favour of converting all the
tests because we can keep writing tests using OUnit 1.x style, making them
backportable to old build environments without OUnit2 (and without this patch).

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>