Select resources when there are nil in MetricRollups records

In this PR ManageIQ#11648 we
introduced selecting rates according to first MetricRollup
record of group. We can do it because group of these records
belong to one resource.

Selection is based on
MetricRollup#parent_host or parent_ems_cluster or
parent_storage or parent_ems but sometimes this fields in
MetricRollup are nil and it produces empty cells on the
report - it is because proper rate was not selected.

Fix provides that we are selecting parents from
the resource direcly when there are not exists in
MetricRollup.

app/models/metric/chargeback_helper.rb

@@ -17,6 +17,11 @@ def tag_list_reconstruct
   end
 
   def resource_parents
-    [parent_host, parent_ems_cluster, parent_storage, parent_ems, resource.try(:tenant)].compact
+    [parent_host || resource.try(:host),
+     parent_ems_cluster || resource.try(:ems_cluster),
+     parent_storage || resource.try(:storage),
+     parent_ems || resource.try(:ext_management_system),
+     resource.try(:tenant)
+    ].compact
   end
 end