fix SSL_do_handshake tls error

56#56: *8262995 SSL_do_handshake() failed (SSL: error:0A00010B:SSL routines::wrong version number) while SSL handshaking to upstream, client: xx, server: yy,

这个报错是因为转发到的后端证书错误
nginx中有配置proxy_ssl_server_name来修复这个问题:

Syntax: 	proxy_ssl_server_name on | off;
Default: 	
 
proxy_ssl_server_name off;
 
Context: 	http, server, location
 
This directive appeared in version 1.7.0.
 
Enables or disables passing of the server name through TLS Server Name Indication extension (SNI, RFC 6066) when establishing a connection with the proxied HTTPS server. 

默认off，配置on即可解决这个问题，跟tls版本没关系。