Solve possible deadlock in ChunkDistributor

[elfenpiff]

Required information

Taken from todo in chunk_distributor.inl: currently we have a deadlock / mutex destroy vulnerability if the ThreadSafePolicy is used and a sending application dies when having the lock for sending. If the RouDi daemon wants to cleanup or does discovery changes we have a deadlock or an exception when destroying the mutex As long as we don't have a multi-threaded lock-free ChunkDistributor or another concept we die here