Fixes a bug when iterating on paths

This fixes the incorrect implementation of iterating on file/directory
paths.

Differential Review: http://llvm-reviews.chandlerc.com/D1277


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188183 91177308-0d34-0410-b5e6-96231b3b80d8