Test that switching versions on renego is illegal.

We handle this correctly but never wrote a test for it. Noticed this in
chatting about the second ClientHello.version bug workaround with Eric
Rescorla.

Change-Id: I09bc6c995d07c0f2c9936031b52c3c639ed3695e
Reviewed-on: https://boringssl-review.googlesource.com/9154
Reviewed-by: Steven Valdez <svaldez@google.com>
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/test/runner/common.go b/ssl/test/runner/common.go
index aca308c..b6befe4 100644
--- a/ssl/test/runner/common.go
+++ b/ssl/test/runner/common.go
@@ -606,6 +606,10 @@
 	// peer.
 	NegotiateVersion uint16
 
+	// NegotiateVersionOnRenego, if non-zero, causes the server to negotiate
+	// the specified TLS version on renegotiation rather than retaining it.
+	NegotiateVersionOnRenego uint16
+
 	// ExpectFalseStart causes the server to, on full handshakes,
 	// expect the peer to False Start; the server Finished message
 	// isn't sent until we receive an application data record