Send correct fatal alert the renegotation extension fails to match.

https://tools.ietf.org/html/rfc5746#section-3.4 says that
handshake_failure is the correct alert to send, but we were sending
illegal_parameter.

Change-Id: Ife951c5951f6f8e4c31a3f2f57307bfed1c24561
Reviewed-on: https://boringssl-review.googlesource.com/18408
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/ssl/t1_lib.cc b/ssl/t1_lib.cc
index 19f256d..283f22c 100644
--- a/ssl/t1_lib.cc
+++ b/ssl/t1_lib.cc
@@ -802,7 +802,7 @@
 #endif
   if (!ok) {
     OPENSSL_PUT_ERROR(SSL, SSL_R_RENEGOTIATION_MISMATCH);
-    *out_alert = SSL_AD_ILLEGAL_PARAMETER;
+    *out_alert = SSL_AD_HANDSHAKE_FAILURE;
     return 0;
   }
   ssl->s3->send_connection_binding = 1;