Add support for KVM Steal-Time registration

[lmr]

I'm moving issue:

https://github.com/autotest/autotest/issues/417

The original text by @anantyog is:

Steal time is the time that a virtual CPU waits for a real CPU while the hypervisor is servicing another virtual processor. KVM virtual machines can now calculate and report steal time, visible through tools like 'top' and 'vmstat', which provides a guest accurate CPU utilization data.

Run stress test on the guest, steal time in guest must provide the accurate data depending on the stress genarted on the guests and host

1.use taskset -c 1 ....boot two guest on host 2.Add 100% cpu load in both guest.

e.g run following command in guest:

for ((;;)); do x=1; done

3.run top on both guest steal time around 50% on both guests