Ignore azure_maintenance database in postgres check to avoid permission error (DataDog#2310)

Ignore 'azure_maintenance' db to avoid permission error

Author: MargotLepizzera

postgres/datadog_checks/postgres/postgres.py

@@ -496,7 +496,8 @@ def _get_instance_metrics(self, key, db, database_size_metrics, collect_default_
             'query': "SELECT datname, %s "
             "FROM pg_stat_database "
             "WHERE datname not ilike 'template%%' "
-            "  AND datname not ilike 'rdsadmin' ",
+            "  AND datname not ilike 'rdsadmin' "
+            "  AND datname not ilike 'azure_maintenance' ",
             'relation': False,
         }