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

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

in this patchset, follow changes has been introduced:
1. Add a new flag TrustedService in ovf file to record whether the VM is exported from a trusted cluster.
2. Code cleanup.

Change-Id: I0f42f848798706be58acf1291c1841da1135d76d
Signed-off-by: Jimmy <gang.wei@intel.com>
Signed-off-by: Zhang Lijuan <lijuan.zhang@intel.com>
Signed-off-by: Dave Chen <wei.d.chen@intel.com>
Signed-off-by: Quan Xu <quan.xu@intel.com>
Signed-off-by: Dave Chen <wei.d.chen@intel.com>