cmdtests: add update_outputs
cmdtests: add update_outputs

This is to make it easier to update cmdtest .stdout and .stderr files when they
have changed. Less manual work.

Signed-off-by: Kalle Valo <7081a7d99b8c74c0698a728df19e3915a995d7e1@codeaurora.org>

kvalo/pwcli,kvalo/pwcli