Removing extra SSL_shutdown() call.

mongoose.c

@@ -4864,7 +4864,6 @@ static void close_connection(struct mg_connection *conn) {
   if (conn->ssl != NULL) {
     // Run SSL_shutdown twice to ensure completly close SSL connection
     SSL_shutdown(conn->ssl);
-    SSL_shutdown(conn->ssl);
     SSL_free(conn->ssl);
     conn->ssl = NULL;
   }