Bug 1053940 - docker-worker: Encrypted environment variables

One open issue is the management of the gpg keys. Currently they are hard-coded.
You error seems to flow all the way to the [public task specific log](https://github.com/russnicoletti/docker-worker/blob/bug-1053940/lib/task.js#L591-L593). 
The same goes for `encryptedData.created` and `encryptedData.deadline`. 

We should not expose secret data in public logs; I think the security of GPG is pretty good, so it's probably not a big attack vector; but as a rule of thumb don't expose protected data. When checks here fail, we need to assume the worst. Also no need to do all checks, if one check fail, bail - I'm okay with providing an attacker with as little information as possible. Just enough that legitimate developers can debug it, or ask us for help.

A good way around this is to debug like this:
```js
  var incidentId = uuid.v4();
  debug("the created date in the env payload is in the future, " +
        "now:  %s env created date: %s; incidentId: %s",
        Date.now(), encryptedData.created, incidentId);
  throw new Error("the created date in the env payload is in the future, incidentId: " + incidentId);
```

This way, the `incidentId` can be found in logs on papertrail, these are not public... 

**Note** I still wouldn't log the payload of the encrypted env var to papertrail though.