Bug 1100905 — Remove redis keys wildcard lookups.

https://bugzilla.mozilla.org/show_bug.cgi?id=1100905
looks like you can use multi here too... 
```js
self._client.multi(
  ['HDEL', 'roomparticipant.' + roomToken, hawkIdHmac],
  ['DEL', 'roomparticipant_access_token.' + roomToken + '.' + hawkIdHmac]
).exec(callback);
```
...is also a supported notation, right?