Default to SSLv23 (autonegotiate), fixes #5870

[hdm]

This changes the default SSL/TLS version to "SSLv23", which in OpenSSL parlance means "autonegotiate". This is necessary to fix #5870. A small amount of cleanup is included in this patch as well, notably:

• Only try a single SSL/TLS version. This is functionally the same as before, since the previous version arrays only included one item. Retrying different SSL/TLS versions on the same socket is unlikely to work in many cases.
• Remove commented out dead code related to sync_close

[bcook-r7]

LGTM:

openssl s_server -tls1_2
WARNING: can't open config file: /usr/local/etc/ssl/openssl.cnf
Using auto DH parameters
Using default temp ECDH parameters
ACCEPT
bad gethostbyaddr
-----BEGIN SSL SESSION PARAMETERS-----
MFUCAQECAgMDBALAMAQABDBy7eehsE6G4P0ifBid1eaP6i0iQmffryWQAd7npyxE
xuY49OV1R99QGc+eDKIW0WahBgIEVeYy0aIEAgIcIKQGBAQBAAAA
-----END SSL SESSION PARAMETERS-----
Shared ciphers:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-DSS-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA256:DHE-RSA-AES256-SHA:DHE-DSS-AES256-SHA:DHE-RSA-CAMELLIA256-SHA:DHE-DSS-CAMELLIA256-SHA:ECDH-RSA-AES256-GCM-SHA384:ECDH-ECDSA-AES256-GCM-SHA384:ECDH-RSA-AES256-SHA384:ECDH-ECDSA-AES256-SHA384:ECDH-RSA-AES256-SHA:ECDH-ECDSA-AES256-SHA:AES256-GCM-SHA384:AES256-SHA256:AES256-SHA:CAMELLIA256-SHA:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:DHE-DSS-AES128-GCM-SHA256:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES128-SHA256:DHE-DSS-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA:DHE-RSA-CAMELLIA128-SHA:DHE-DSS-CAMELLIA128-SHA:ECDH-RSA-AES128-GCM-SHA256:ECDH-ECDSA-AES128-GCM-SHA256:ECDH-RSA-AES128-SHA256:ECDH-ECDSA-AES128-SHA256:ECDH-RSA-AES128-SHA:ECDH-ECDSA-AES128-SHA
CIPHER is ECDHE-RSA-AES256-GCM-SHA384
Secure Renegotiation IS supported
GET /aspnet_client HTTP/1.1
Host: 192.168.56.1:4433
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)
Authorization: NTLM TlRMTVNTUAABAAAAB4IIogAAAAAAAAAAAAAAAAAAAAAGAbEdAAAADw==
Content-Type: application/x-www-form-urlencoded
Content-Length: 0

[bcook-r7]

Thanks for the update @hmoore-r7