Make java benchmarks runnable out of the box again

Added missing bench.jar file back to the image.
Fixed an obsolete description in the README file.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
virtio-net: Remove unused page size constant

The page_size constant is not used in the code so lets just remove it.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>