Investigate and fix `TestPeerReputation` which randomly failed

[Logs](https://github.com/ChainSafe/gossamer/runs/6258382606?check_suite_focus=true) (pretty much development branch untouched Go code)

```go
--- FAIL: TestPeerReputation (6.18s)
host_test.go:682:
Error Trace: host_test.go:682
Error: Not equal:
expected: 1
actual : 0
Test: TestPeerReputation
```

It might be due to either:

- flaky time-dependent test; or
- `2022-05-02T14:02:18.399Z ERROR peerstore/ds pstoreds/keybook.go:85 error while updating pubkey in datastore for peer 12D3KooWS5fL7GA4WHDZxUx2DcbNBTWdGH5BZWeWWdQcQAqYhUM6: datastore closed`