Go client script no longer needed on akaros side.
Add cpio as a default program built for busybox

Dont forget to reconfigure and reinstall busybox with the cpio option
enabled if you don't want to reapply the default config.
Add ability to run init script through config var

There is now a config variable that allows you to specify a script to
run after the kernel has booted.  Use this variable to specify the path
to a script, followed by any arguments you want to pass it.  There is
default init.sh script that has been put in kfs/bin that simply calls
ifconfig and then drops you into busybox.

If this config variable isn't set, we still run the manager function, for
backwards compatibility reasons.  Eventually we want to do away with the
managers altogether, but the way jenkins is set up currently prevents
this without some major changes.  Once we have something like Ron's #z
device, we will be able to do away the menager completely since jenkins
will be able to use #z to run kernel tests from userspace.