Sorting terms agg by sub-aggegation doesn't respect asc/desc when executing on a single shard

[uboness]

As reported on #4643, when trying to sort terms aggregation based on sub metric aggregation, the asc/desc order is not respected. For example:

{
  "aggs": {
    "fieldValues": {
      "terms": {
        "field": "name.field",
        "order": {
          "totalAmount": "desc"
        }
      },
      "aggs": {
        "totalAmount": {
          "sum": {
            "field": "amount"
          }
        }
      }
    }
  },
  "size": 0
}

In the example above, when executing on a single shard, the terms are always sorted in an ascending order.

[uboness]

@benatwork99 fyi, thx for your patience

[benatwork99]

@uboness Thank you for the quick fix! Looking forward to RC2 :)