Ignore the session when setting SNI in s_client

As per this comment:

https://github.com/openssl/openssl/issues/4496#issuecomment-337767145

Since the server is entitled to reject our session our ClientHello
should include everything that we would want if a full handshake were
to happen. Therefore we shouldn't use the session as a source of
information for setting SNI.
Reviewed-by: NBen Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/4738)

apps/s_client.c

@@ -1923,18 +1923,7 @@ int s_client_main(int argc, char **argv)
             ERR_print_errors(bio_err);
             goto end;
         }
-        /* By default the SNI should be the same as was set in the session */
-        if (!noservername && servername == NULL) {
-            servername = SSL_SESSION_get0_hostname(sess);
 
-            if (servername == NULL) {
-                /*
-                 * Force no SNI to be sent so we are consistent with the
-                 * session.
-                 */
-                noservername = 1;
-            }
-        }
         SSL_SESSION_free(sess);
     }
 

test/recipes/70-test_sslmessages.t

@@ -164,8 +164,7 @@ $proxy->clientflags("-no_tls1_3 -sess_in ".$session);
 $proxy->clientstart();
 checkhandshake($proxy, checkhandshake::RESUME_HANDSHAKE,
                checkhandshake::DEFAULT_EXTENSIONS
-               & ~checkhandshake::SESSION_TICKET_SRV_EXTENSION
-               & ~checkhandshake::SERVER_NAME_CLI_EXTENSION,
+               & ~checkhandshake::SESSION_TICKET_SRV_EXTENSION,
                "Resumption handshake test");
 unlink $session;
 

test/recipes/70-test_tls13messages.t

@@ -167,8 +167,7 @@ $proxy->clientstart();
 checkhandshake($proxy, checkhandshake::RESUME_HANDSHAKE,
                (checkhandshake::DEFAULT_EXTENSIONS
                 | checkhandshake::PSK_CLI_EXTENSION
-                | checkhandshake::PSK_SRV_EXTENSION)
-               & ~checkhandshake::SERVER_NAME_CLI_EXTENSION,
+                | checkhandshake::PSK_SRV_EXTENSION),
                "Resumption handshake test");
 
 #Test 3: A status_request handshake (client request only)
@@ -312,8 +311,7 @@ checkhandshake($proxy, checkhandshake::HRR_RESUME_HANDSHAKE,
                (checkhandshake::DEFAULT_EXTENSIONS
                 | checkhandshake::KEY_SHARE_HRR_EXTENSION
                 | checkhandshake::PSK_CLI_EXTENSION
-                | checkhandshake::PSK_SRV_EXTENSION)
-               & ~checkhandshake::SERVER_NAME_CLI_EXTENSION,
+                | checkhandshake::PSK_SRV_EXTENSION),
                "Resumption handshake with HRR test");
 
 #Test 16: Acceptable but non preferred key_share