Remove SSL_OP_TLS_ROLLBACK_BUG.

It's not part of SSL_OP_ALL and is unused, so remove it. Add a test that
asserts the version check works.

Change-Id: I917516594ec5a4998a8316782f035697c33d99b0
Reviewed-on: https://boringssl-review.googlesource.com/1418
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/runner/key_agreement.go b/ssl/test/runner/key_agreement.go
index 0e29d63..929eb06 100644
--- a/ssl/test/runner/key_agreement.go
+++ b/ssl/test/runner/key_agreement.go
@@ -70,8 +70,12 @@
 
 func (ka rsaKeyAgreement) generateClientKeyExchange(config *Config, clientHello *clientHelloMsg, cert *x509.Certificate) ([]byte, *clientKeyExchangeMsg, error) {
 	preMasterSecret := make([]byte, 48)
-	preMasterSecret[0] = byte(clientHello.vers >> 8)
-	preMasterSecret[1] = byte(clientHello.vers)
+	vers := clientHello.vers
+	if config.Bugs.RsaClientKeyExchangeVersion != 0 {
+		vers = config.Bugs.RsaClientKeyExchangeVersion
+	}
+	preMasterSecret[0] = byte(vers >> 8)
+	preMasterSecret[1] = byte(vers)
 	_, err := io.ReadFull(config.rand(), preMasterSecret[2:])
 	if err != nil {
 		return nil, nil, err