clang-format: Improve recovery from enums with errors.

Before:
  namespace n {
  enum Type {
    One,
    Two, // missing };
    int i;
  } void g() {
  }

After:
  namespace n {
  enum Type {
    One,
    Two, // missing };
    int i;
  }
  void g() {}

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189662 91177308-0d34-0410-b5e6-96231b3b80d8