[libvirt] [PATCH] qemu: do upfront check for vcpupids being null when querying pinning

[Serge Hallyn]

Quoting Serge Hallyn (serge.hallyn at ubuntu.com):
> Quoting Daniel P. Berrange (berrange at redhat.com):
> > The qemuDomainHelperGetVcpus attempted to report an error when the
> > vcpupids info was NULL. Unfortunately earlier code would clamp the
> > value of 'maxinfo' to 0 when nvcpupids was 0, so the error reporting
> > would end up being skipped.
> > 
> > This lead to 'virsh vcpuinfo <dom>' just returning an empty list
> > instead of giving the user a clear error.
> > ---
> 
> Cool, thanks.  (haven't kicked off a test yet but it looks correct :)
> 
> Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>

and

Tested-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>