vmstat: add guest field

In cpu line of /proc/stat guest and niced guest fields are available
since 2009, linux-2.6.32. It is useful statistics if the system runs
as a kvm hypervisor.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
1 job for cpu-guest-stat in 2 minutes (queued for 34 minutes and 56 seconds)
latest
Status Job ID Name Coverage
  Test
passed #2522291
MakeCheck

00:02:00