[libvirt] [RFC] Add a new feild to qemud_save_header to tell if the saved image is corrupt

If one tries to restore a domain from a corrupt save image, we blindly goes forward to restore from it, this can cause many different errors, depending on how much the image is saved. E.g. https://bugzilla.redhat.com/show_bug.cgi?id=730750 So I'm thinking if we can introduce a new feild to struct qemud_save_header, such as "bool complete;", and set it true if succeeded to save the image, false if not. So that could do some checking while trying to open the image (qemuDomainSaveImageOpen), and quit early if "complete" is false, with a sensiable error message. Thought? Thanks Osier