Fix logic around when to send an HRR based on cookies

Reviewed-by: Ben Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/4435)
diff --git a/ssl/statem/extensions_srvr.c b/ssl/statem/extensions_srvr.c
index 16f1b85..83cd363 100644
--- a/ssl/statem/extensions_srvr.c
+++ b/ssl/statem/extensions_srvr.c
@@ -895,6 +895,8 @@
     /* Act as if this ClientHello came after a HelloRetryRequest */
     s->hello_retry_request = 1;
 
+    s->ext.cookieok = 1;
+
     return 1;
 }