Query nodes that are unreachable are not taken out of rotation

If a query request targets a node that is offline, the node should be:
1 - Marked as down
2 - Taken out of rotation
3 - Timer started for heartbeat checks
4 - If heartbeat returns true, then brought back into rotation

No requests should be tried on the node until it is back online. If the initial query failed, it should be retried on the other nodes until successful. If no nodes are available, then it should fail with the original exception.