test/py: vboot: Remove stderr redirect from openssl command

test/py: vboot: Remove stderr redirect from openssl command

The openssl command specified in test_with_algo() ultimately ends up
being run by RunAndLog::run(), which uses it to construct a Popen object
with the default shell=False. The stderr redirect in the command is
therefore simply passed to openssl as an argument. With at least openssl
1.1.0f this causes openssl, and therefore test_vboot, to fail with:

  genpkey: Use -help for summary.
  Exit code: 1

Any stderr output ought to be captured & stored in the RunAndLog
object's output field and returned from run() via run_and_log() to
test_with_algo() which then ignores it anyway, so we can drop the
shell-like redirection with no ill effects. With this fix test_vboot now
passes for me.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>