berserker: Need better loop detection

[SkyperTHC]

doing everything just in memory without even touching /dev/shm is tricky and loop-detection wont work when the ssh-path branches:

A -> A is detected A -> B -> A is detected A -> B -> B is detected

A -> B -> C A -> C is NOT detected.

This is because the LOOP-DB is only available OUTSIDE the main for-loop.

Changing this to marking a file in /dev/shm would fix this and also simplify parallel execution to speed up the berserker.