qemu: Clean up ret in qemuDomainSaveMemory and qemuDomainSaveInternal
qemu: Clean up ret in qemuDomainSaveMemory and qemuDomainSaveInternal

As it turns out, ret can only be 0 or -1, so rather than have some comparisons
be "ret < 0" and others be "ret != 0", make them all "ret < 0".

datto/libvirt,libvirt/libvirt,andreabolognani/libvirt,zippy2/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,rlaager/libvirt,jfehlig/libvirt,jardasgit/libvirt,agx/libvirt,crobinso/libvirt,olafhering/libvirt,nertpinx/libvirt,nertpinx/libvirt,andreabolognani/libvirt,taget/libvirt,taget/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,eskultety/libvirt,VenkatDatta/libvirt,agx/libvirt,eskultety/libvirt,zippy2/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,zippy2/libvirt,fabianfreyer/libvirt,taget/libvirt,datto/libvirt,olafhering/libvirt,datto/libvirt,olafhering/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,eskultety/libvirt,eskultety/libvirt,jfehlig/libvirt,libvirt/libvirt,agx/libvirt,nertpinx/libvirt,crobinso/libvirt,datto/libvirt,fabianfreyer/libvirt,taget/libvirt,taget/libvirt,crobinso/libvirt,agx/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,libvirt/libvirt,fabianfreyer/libvirt,zippy2/libvirt,agx/libvirt,nertpinx/libvirt,rlaager/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,rlaager/libvirt,crobinso/libvirt,jardasgit/libvirt,rlaager/libvirt,andreabolognani/libvirt,nertpinx/libvirt,olafhering/libvirt,libvirt/libvirt,rlaager/libvirt,eskultety/libvirt,datto/libvirt