aggregate_data_free_by_tier list_nodes fine tuning

[jeniawhite]

Environment info

• Version: VERSION
• Deployment: AZURE|ESX|AWS|GCLOUD|DEV|VBOX
• Customer: NAME

Actual behavior

• The request to list_nodes is repeating for every tier on the same pools.
• The default_pool (or other common pool) is very likely to be requested for every bucket.
• We should collect the pools we want to list before and ask them uniq once.
• In addition, we can use the auth_token from the req.auth_token since we are in a context of an rpc request there.

Expected behavior

Steps to reproduce

Screenshots or Logs or other output that would be helpful

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