Ensure that when mod_ssl is unloaded, libcrypto doesn't
still have the thread_id callback pointing at a mod_ssl
function.

This can cause headaches like #97207

--- httpd-2.0.47/modules/ssl/ssl_util.c.sslcleanup
+++ httpd-2.0.47/modules/ssl/ssl_util.c
@@ -455,6 +455,8 @@
 {
     CRYPTO_set_locking_callback(NULL);
 
+    CRYPTO_set_id_callback(NULL);
+
     /* Let the registered mutex cleanups do their own thing 
      */
     return APR_SUCCESS;