Rebalance shows as completed when there is an error fetching the rebalance progress

When ns_server has an error fetching the rebalance progress, the tasks endpoint will return a task including following fields (among others):

{

  "type": "rebalance",

  "status": "notRunning",

  "statusIsStale": true,

  "masterRequestTimedOut": true  // Or false, depending on the error

}

Specifically, if we see "statusIsStale": true, this means there was an error getting the rebalance status, so "notRunning" is not necessarily correct.

Currently, the UI interprets this as a completed rebalance, giving a misleading indication. See MB-60118 for an example.

The expected behaviour would be for the UI to show the previous task status, since in the worst case the UI would have out-dated information, rather than entirely incorrect. Additionally, the stale status could be shown in the UI, making it clear that the information is likely to be out of date.