Fix non-existing gauge duplicate

In Elasticsearch 7.x hits,total field
is not integer, but dictionary causing
failure to create proper gauge,
which is registered in collector
causing duplicate error.

For other cases - reregister Gauge collector

Change-Id: Ied8cc69a4ea4c1482b3670e2fab9a66ff0d386e7
Related-bug: PROD-32451
diff --git a/prometheus_es_exporter/parser.py b/prometheus_es_exporter/parser.py
index 9ec59fe..f978cf2 100644
--- a/prometheus_es_exporter/parser.py
+++ b/prometheus_es_exporter/parser.py
@@ -80,7 +80,10 @@
     result = []
 
     if not response['timed_out']:
-        result.append((metric + ['hits'], {}, response['hits']['total']))
+        hits_total = response['hits']['total']
+        if isinstance(hits_total, dict):
+            hits_total = hits_total.get('value', 0)
+        result.append((metric + ['hits'], {}, hits_total))
         result.append((metric + ['took', 'milliseconds'], {}, response['took']))
 
         if 'aggregations' in response.keys():