Linux: Ignore sockets with unknown id
Linux: Ignore sockets with unknown id

Reported by Greg Bauer, it was creating invalid sockets
on Power7 machines.

git-svn-id: 14be032f8f42541b1a281b51ae8ea69814daf20e@2151 4b44e086-7f34-40ce-a3bd-00e031736276

BlueBrain/hwloc,BlueBrain/hwloc,BlueBrain/hwloc,BlueBrain/hwloc