Add tests for certificate mismatch.

Cover another mildly interesting error case.

Change-Id: Ice773af79f5e03f39f0cd2a9e158bae03e065392
Reviewed-on: https://boringssl-review.googlesource.com/2841
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/runner/common.go b/ssl/test/runner/common.go
index 443d464..774c7a3 100644
--- a/ssl/test/runner/common.go
+++ b/ssl/test/runner/common.go
@@ -594,6 +594,11 @@
 	// MaxPacketLength, if non-zero, is the maximum acceptable size for a
 	// packet.
 	MaxPacketLength int
+
+	// SendCipherSuite, if non-zero, is the cipher suite value that the
+	// server will send in the ServerHello. This does not affect the cipher
+	// the server believes it has actually negotiated.
+	SendCipherSuite uint16
 }
 
 func (c *Config) serverInit() {