SSL: avoid calling SSL_shutdown() during handshake (ticket #901).
SSL: avoid calling SSL_shutdown() during handshake (ticket #901).

This fixes "called a function you should not call" and
"shutdown while in init" errors as observed with OpenSSL 1.0.2f
due to changes in how OpenSSL handles SSL_shutdown() during
SSL handshakes.

firebase/nginx,firebase/nginx,firebase/nginx,firebase/nginx