Change arc-cxx11-init-list.mm to work with upcoming SCEV changes.

Summary:
The store being checked for in arc-cxx11-init-list.mm is a store to an
unescaped alloca.  After an uncoming change to ScalarEvolution, LLVM is
able to elide the store, so adjust the test accordingly.

Reviewers: compnerd

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D13183

llvm-svn: 248632