* devices.in (dev_storage): Map /dev/random and /dev/urandom to
\Device\Null.
* devices.cc: Regenerate.
* fhandler.h (fhandler_dev_random::open): Drop declaration.
(fhandler_dev_random::close): Ditto.
(fhandler_dev_random::crypt_gen_random): Convert to static method.
* fhandler_random.cc (fhandler_dev_random::open): Remove so that default
fhandler_base::open is used to open \Device\Null.
(fhandler_dev_random::close): Ditto.
* fhandler_socket.cc (entropy_source): Delete.
(fhandler_socket::af_local_set_secret): Remove entropy_source code and
call fhandler_dev_random::crypt_gen_random directly instead.