Switch the default TLS 1.3 variant to tls13_rfc.

Update-Note: If not explicitly configured to use tls13_all, callers that enable
TLS 1.3 will now only enable the final standard version.

Change-Id: Ifcfc65a9d8782c983df6e002925e8f77f45b6e53
Reviewed-on: https://boringssl-review.googlesource.com/31384
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/tool/server.cc b/tool/server.cc
index 824538a..c4b23bf 100644
--- a/tool/server.cc
+++ b/tool/server.cc
@@ -161,6 +161,10 @@
     *out = tls13_rfc;
     return true;
   }
+  if (in == "all") {
+    *out = tls13_all;
+    return true;
+  }
   return false;
 }