NMT: MetaspaceSnapshot::snapshot uses wrong enum

While reviewing Richard found:

"This is not part of your change, but aren't ClassType and NonClassType mixed up in the body of MetaspaceSnapshot::snapshot method?"

and it looks like it:

void MetaspaceSnapshot::snapshot(MetaspaceSnapshot& mss) {
  snapshot(Metaspace::ClassType, mss);
  if (Metaspace::using_class_space()) {
    snapshot(Metaspace::NonClassType, mss);
  }
}