Fix some bugs:
Fix some bugs:

 - modify_arg_for_default_detection was not actually succeeding in modifying
   the kwargs it was called with
 - it should be good enough for the default detector to notice --dry-run and
   pass that to the real conf, we don't need to play with .server as well...

mitnk/letsencrypt,jtl999/certbot,dietsche/letsencrypt,letsencrypt/letsencrypt,TheBoegl/letsencrypt,thanatos/lets-encrypt-preview,wteiken/letsencrypt,bsmr-misc-forks/letsencrypt,lmcro/letsencrypt,TheBoegl/letsencrypt,letsencrypt/letsencrypt,brentdax/letsencrypt,jsha/letsencrypt,mitnk/letsencrypt,stweil/letsencrypt,dietsche/letsencrypt,thanatos/lets-encrypt-preview,bsmr-misc-forks/letsencrypt,stweil/letsencrypt,brentdax/letsencrypt,DavidGarciaCat/letsencrypt,lmcro/letsencrypt,DavidGarciaCat/letsencrypt,jsha/letsencrypt,jtl999/certbot,wteiken/letsencrypt