Description of problem:
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Sometimes clusters with the same name can exist in multiple providers. 
E.g. My appliance is managing vSphere 6.0 and vSphere 6.5 and "Cluster" exists in both these providers.

In such a scenario,the Chargeback rate assignment page only shows one of the two clusters.


Version-Release number of selected component (if applicable):
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5.8


How reproducible:
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Always


Steps to Reproduce:
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1. Manage two providers that have at least 1 cluster with the same name.
2. Navigate to the Compute Rate Assignment page.
4. In the Assign to dropdwon, select 'Selected Cluster/Deployment Roles'.
5. The Selections section only shows "Cluster" once and does not indicate to which provider the cluster belongs.


Actual results:
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'Cluster' is shown only once and there is no way to tell to which provider it belongs.


Expected results:
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There should be two clusters showing up and ideally they should indicate to which provider they belong (maybe something like "<provider>/<Cluster name>"


Additional info:
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