[Libvirt-cim] [PATCH 0 of 2] Add VirtualSystemSnapshotService

[Dan Smith]

This adds basic support for the VirtualSystemSnapshotService.

Since the service seems to assume that a system can be snapshotted while
running (which Xen cannot do), we provide a terminal snapshot and fake a
running snapshot by doing a save/resume.

Still to be done is adding the Capabilities support, as well as making
the VSSD provider expose an additional VSSD for the snapshot, as required
by the SVP.