The goal here is that save-image-dumpxml fed back to
save-image-define should not change the save file; anywhere that
this is not the case is probably a bug in domain_conf.c.

* src/qemu/qemu_driver.c (qemuDomainSaveImageGetXMLDesc)
(qemuDomainSaveImageDefineXML): New functions.
(qemuDomainSaveImageOpen): Add parameter.
(qemuDomainRestoreFlags, qemuDomainObjRestore): Adjust clients.