Issue #3239: Checking signal's default action before handling it.
Issue #3239: Checking signal's default action before handling it.

lmcro/letsencrypt,jsha/letsencrypt,jtl999/certbot,letsencrypt/letsencrypt,lmcro/letsencrypt,jsha/letsencrypt,jtl999/certbot,stweil/letsencrypt,bsmr-misc-forks/letsencrypt,bsmr-misc-forks/letsencrypt,letsencrypt/letsencrypt,stweil/letsencrypt