qemu: forbid negative blkio values
qemu: forbid negative blkio values

Partially resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1131306

Signed-off-by: Martin Kletzander <e82f23e74d43760279ebcc505dac4ae70d5627d0@redhat.com>

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