cli_test: _call() now allows stdout content inspection
cli_test: _call() now allows stdout content inspection

wteiken/letsencrypt,bsmr-misc-forks/letsencrypt,brentdax/letsencrypt,jsha/letsencrypt,jtl999/certbot,stweil/letsencrypt,letsencrypt/letsencrypt,letsencrypt/letsencrypt,wteiken/letsencrypt,dietsche/letsencrypt,jtl999/certbot,mitnk/letsencrypt,jsha/letsencrypt,lmcro/letsencrypt,lmcro/letsencrypt,stweil/letsencrypt,dietsche/letsencrypt,DavidGarciaCat/letsencrypt,DavidGarciaCat/letsencrypt,brentdax/letsencrypt,bsmr-misc-forks/letsencrypt,mitnk/letsencrypt