Fix the tests for the fuzzer mode.

It's useful to make sure our fuzzer mode works. Not all tests pass, but most
do. (Notably the negative tests for everything we've disabled don't work.) We
can also use then use runner to record fuzzer-mode transcripts with the ciphers
correctly nulled.

Change-Id: Ie41230d654970ce6cf612c0a9d3adf01005522c6
Reviewed-on: https://boringssl-review.googlesource.com/7288
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/runner/conn.go b/ssl/test/runner/conn.go
index cb60a92..5a19c28 100644
--- a/ssl/test/runner/conn.go
+++ b/ssl/test/runner/conn.go
@@ -189,6 +189,11 @@
 	hc.nextMac = nil
 	hc.config = config
 	hc.incEpoch()
+
+	if config.Bugs.NullAllCiphers {
+		hc.cipher = nil
+		hc.mac = nil
+	}
 	return nil
 }