Read hits.total.value to get number of hits (#15728)

This should fix test_management.py under Python3. An object was being returned but
the test was expecting to get a number. The format of the Elasticsearch response changed
for the "track_total_hits" enhancement, but this wasn't updated.

x-pack/libbeat/tests/system/test_management.py

@@ -282,7 +282,7 @@ def random_index(self):
  def check_document_count(self, index, count):
  try:
  self.es.indices.refresh(index=index)
- return self.es.search(index=index, body={"query": {"match_all": {}}})['hits']['total'] >= count
+ return self.es.search(index=index, body={"query": {"match_all": {}}})['hits']['total']['value'] >= count
  except:
  return False