SSL: clear protocol options.
SSL: clear protocol options.

LibreSSL 2.1.1+ started to set SSL_OP_NO_SSLv3 option by default on
new contexts.  This makes sure to clear it to make it possible to use SSLv3
with LibreSSL if enabled in nginx config.

Prodded by Kuramoto Eiji.

hy0kl/nginx,hy0kl/nginx,hy0kl/nginx