Fix inconsistency caused by the autopilot StatsFetcher #4528
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This fix came out of looking into an issue in the enterprise redundancy zones feature - the reads on the RPC result channels in the stats fetcher were being affected by a single failed outgoing RPC (doing a select against multiple channels does not give priority to the first channel) which was incorrectly marking other servers as failed/unhealthy. This caused some inconsistencies with autopilot promoting servers, namely around redundancy zones where the current voter in a zone could be marked as unhealthy.
Fixing this also exposed that the restriction around removing dead servers (
removalCount < peers/2) shouldn't apply in the case of non-voting servers, since there's no downside to removing them as they can't affect the quorum.