BUG/MAJOR: ssl: ssl_sock was not fully initialized.

BUG/MAJOR: ssl: ssl_sock was not fully initialized.

'ssl_sock' wasn't fully initialized so a new session can inherit some
flags from an old one.

This causes some fetches, related to client's certificate presence or
its verify status and errors, returning erroneous values.

This issue could generate other unexpected behaviors because a new
session could also inherit other flags such as SSL_SOCK_ST_FL_16K_WBFSIZE,
SSL_SOCK_SEND_UNLIMITED, or SSL_SOCK_RECV_HEARTBEAT from an old session.

This must be backported to 2.0 but it's useless for previous.