Don't set SSL_MODE_NO_AUTO_CHAIN during renegotiation.

If during the renegotiation's ClientHello a client passes:

 if (tor_tls_client_is_using_v2_ciphers(ssl, ADDR(tls))) {

in tor_tls_server_info_callback() (or tor_tls_got_client_hello() in master), we don't send a full certificate chain to the client.

The above if statement should only be examined during the initial SSL handshake.

There was already a

/*XXXX_TLS keep this from happening more than once! */ 

comment that never got implemented.