engine:Trusted Compute Pools - Open Attestation integration with oVirt engine

Detailed description: http://wiki.ovirt.org/Trusted_compute_pools

Added logging when:
 1) Creating a template with different trust value from the original vm
 2) Importing trusted template to an untrusted cluster
 3) changing the trust value of a template

Change-Id: Icf866224c6bdddb3e4cbf56666a8b340213f7c83
Signed-off-by: Gang Wei <gang.wei@intel.com>
Signed-off-by: Emily <lijuan.zhang@intel.com>