Add tests for the old client cert callback.

Also add no-certificate cases to the state machine coverage tests.

Change-Id: I88a80df6f3ea69aabc978dd356abcb9e309e156f
Reviewed-on: https://boringssl-review.googlesource.com/7417
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/ssl/test/test_config.cc b/ssl/test/test_config.cc
index 95c85a8..dfbd380 100644
--- a/ssl/test/test_config.cc
+++ b/ssl/test/test_config.cc
@@ -98,6 +98,8 @@
   { "-p384-only", &TestConfig::p384_only },
   { "-enable-all-curves", &TestConfig::enable_all_curves },
   { "-use-sparse-dh-prime", &TestConfig::use_sparse_dh_prime },
+  { "-use-old-client-cert-callback",
+    &TestConfig::use_old_client_cert_callback },
 };
 
 const Flag<std::string> kStringFlags[] = {