Add cpu model for kvm guest.Now all the kvm guest's cpu model is 'QEMU Virtual CPU version xxx'. This will affect the activation of Windows OS and low performance. I add three mode for user to indicate the guest cpu model.add libvirt version check

Signed-off-by: Wei Zhou <w.zhou@leaseweb.com>
(cherry picked from commit 2903bb5fd9d59803980102854d11e33ebe56088b)
CLOUDSTACK:3594: Fixes related to affinity groups tests. Included two test suites those were missed because there was no decorator for test cases

Signed-off-by: Prasanna Santhanam <tsp@apache.org>