clang-format: Fix indenting corner case with comment and else.

Before:
  if (a) {
    f();
  }
      // or else ..
      else {
    g();
  }

After:
  if (a) {
    f();
  }
  // or else ..
  else {
    g();
  }

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193684 91177308-0d34-0410-b5e6-96231b3b80d8