Fix "glibc detected double free"

Remove extra call to vio_end


sql/mysqld.cc:
  Remove the second call to vio_end as it should only be called once when the server shutdown.

sql/mysqld.cc

@@ -2974,7 +2974,6 @@ static void end_ssl()
     ssl_acceptor_fd= 0;
   }
 #endif /* HAVE_OPENSSL */
-  vio_end();
 }