[MemorySSA] Fix unit tests broken by D26704

Summary:
D26704 fixed the non-determinism in codegen by sorting basic blocks before
iteration so as to have a defined iteration order. As a result we need to fix
the names (numbers) of the temporaries in the following unit tests:
  test/Transforms/Util/MemorySSA/multi-edges.ll
  test/Transforms/Util/MemorySSA/multiple-backedges-hal.ll

Reviewers: dberlin, david2050, mgrang

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26926

llvm-svn: 287575