qemu: avoid double close on domain restore

qemu: avoid double close on domain restore

qemudDomainSaveImageStartVM was evil - it closed the incoming fd
argument on some, but not all, code paths, without informing the
caller about that action.  No wonder that this resulted in
double-closes: https://bugzilla.redhat.com/show_bug.cgi?id=672725

* src/qemu/qemu_driver.c (qemudDomainSaveImageStartVM): Alter
signature, to avoid double-close.
(qemudDomainRestore, qemudDomainObjRestore): Update callers.