Redis aggregator: recover from missing token

Redis aggregator can crash if there are network issues when acquiring a token

```rust
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: PubSub(MissingToken(Io(Custom { kind: Other, error: "failed to lookup address information: Temporary failure in name resolution" })))', src/libcore/result.rs:999:5
```