Fix a miscompilation I introduced in r129652, thanks for Eli for tracking

Fix a miscompilation I introduced in r129652, thanks for Eli for tracking
it down.  we effectively were compile the testcase into:

void test14(int x) {
  switch (x) {
    case 11: break;
    case 42: test14(97);  // fallthrough
    default: test14(42); break;

which is not the same thing at all.  This fixes a miscompilation of
MallocBench/gs seen on the clang-x86_64-linux-fnt buildbot.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129679 91177308-0d34-0410-b5e6-96231b3b80d8