Change hwloc discovery algorithm to print topology only for accessible resources

Change hwloc discovery algorithm to print topology for only accessible
resources, and report uniformity correspondingly, similar to what other topology
discovery algorithms do. Fixes minor inconsistency in total topology reported
and resources used for threads binding in case hwloc used.

Patch by Andrey Churbanov.

Differential Revision: http://reviews.llvm.org/D21389

llvm-svn: 272952