Bug 1053940 - docker-worker: Encrypted environment variables

One open issue is the management of the gpg keys. Currently they are hard-coded.
For the record, sorry I didn't see garndts comment, when recommended the exact opposite later...

It might just be me who cares a bit too much about perfection... At the end of day it doesn't matter.
Returning all errors instead of just the first, makes debugging easier, but also exposes more information to a potential attacker.

**Remark**, including data from encryptedData (like `taskId`) in the error message exposes secret data. On it's own it's hardly an attack vector, but ideally I would prefer to log the secret properties to `debug()` and insert an `incidentId` in both the debug message and the error message. See my comment from before.
(Note this is just a nit, feel free to ignore it)