Merge pull request #1278 from GregP/cloud_topology_power_status_nil

Verify VM power status is not Nil when displaying Cloud Topology
(cherry picked from commit c34bcd6)

https://bugzilla.redhat.com/show_bug.cgi?id=1448207

app/services/cloud_topology_service.rb

@@ -57,7 +57,7 @@ def entity_status(entity)
     if entity.kind_of?(ManageIQ::Providers::CloudManager)
       entity.authentications.blank? ? 'Unknown' : entity.authentications.first.status.try(:capitalize)
     elsif entity.kind_of?(Vm)
-      entity.power_state.capitalize
+      entity.power_state.nil? ? 'Unknown' : entity.power_state.capitalize
     elsif entity.kind_of?(AvailabilityZone)
       'OK'
     elsif entity.kind_of?(CloudTenant)