Add a InvalidChannelIDSignature test.

Apparently we never wrote one of those. Also send a decrypt_error alert
to be consistent with all the other signature checks.

Change-Id: Ib5624d098d1e3086245192cdce92f5df26005064
Reviewed-on: https://boringssl-review.googlesource.com/11180
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/ssl/test/runner/common.go b/ssl/test/runner/common.go
index 715a94b..3300d33 100644
--- a/ssl/test/runner/common.go
+++ b/ssl/test/runner/common.go
@@ -1080,6 +1080,10 @@
 	// TrailingKeyShareData, if true, causes the client key share list to
 	// include a trailing byte.
 	TrailingKeyShareData bool
+
+	// InvalidChannelIDSignature, if true, causes the client to generate an
+	// invalid Channel ID signature.
+	InvalidChannelIDSignature bool
 }
 
 func (c *Config) serverInit() {