Correct the parent testing to avoid the special case where a DIE has a depth of 1

This test was testing that we could correctly find the parent of a DIE, but it was actually just testing the special case where a DIE's depth was 1. This corrects that error by adding an extra level into the the DWARF to ensure that we correctly get the parent by looking for the parent with a depth that is 1 less than the current depth.

Differential Revision: https://reviews.llvm.org/D28261

llvm-svn: 290918