[StaticAnalyzer] Fix failures due to the iteration order of ExplodedNode

Summary:
This fixes failures seen in the reverse iteration builder:
http://lab.llvm.org:8011/builders/reverse-iteration/builds/26

Failing Tests (4):
    Clang :: Analysis/MisusedMovedObject.cpp
    Clang :: Analysis/keychainAPI.m
    Clang :: Analysis/loop-unrolling.cpp
    Clang :: Analysis/malloc.c

Reviewers: zaks.anna, bkramer, chandlerc, krememek, nikhgupt

Reviewed By: zaks.anna

Subscribers: dcoughlin, NoQ, cfe-commits

Differential Revision: https://reviews.llvm.org/D37400

llvm-svn: 312677