FROMLIST: Enable TLS SNI

Upstream submission: ioerror#186

In environments where SSL interception is in place, the SNI field is
often used to figure out whether to enable or disable interception
for a new connection.  Enable SNI on tlsdate requests.

BUG=chromium:400429
TEST=sniff tlsdate's ClientHello message before/after the change, and
     verify that it contains "clients3.google.com" under "Extension:
     server_name"

Change-Id: Ibe6383bd0b9b590a16a08ae8e1b74ee0f401b3f0
Signed-off-by: Kevin Cernekee <cernekee@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/339834
Reviewed-by: Thiemo Nagel <tnagel@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

Author: Kevin Cernekee

src/tlsdate-helper.c

@@ -1187,6 +1187,7 @@ run_ssl (uint32_t *time_map, int time_is_an_illusion, int http)
   }
 
   SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
+  SSL_set_tlsext_host_name (ssl, host);
   verb("V: opening socket to %s:%s", host, port);
   if ( (1 != BIO_set_conn_hostname(s_bio, host)) ||
        (1 != BIO_set_conn_port(s_bio, port)) )