pci: fix a crash when failing to insert the hostbridge parent object
pci: fix a crash when failing to insert the hostbridge parent object

Happens when the PCI locality cpuset conflicts with CPU cpusets
(we fail to insert the resulting group object).
Attach to the root object instead.

Thanks to Nicolas Denoyelle for reporting the problem.

shekkbuilder/hwloc,ggouaillardet/hwloc,ggouaillardet/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc