kvm tools: Improve "kvm list" default output

kvm tools: Improve "kvm list" default output

This patch changes 'kvm list' default output to look as follows:

  [penberg@tux kvm]$ ./kvm list
    PID GUEST
   8156 guest-8156
        default (not running)
        test-box (not running)

Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Acked-by: Sasha Levin <levinsasha928@gmail.com>
Cc: Asias He <asias.hejun@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Pekka Enberg <penberg@kernel.org>