Resolve FIXME:
- This was written when the idea of DebugFCPClient was not born yet. As DebugFCPClient can access the WOT database directly, we don't need to re-synchronize at shutdown for it to be able to check whether the state is valid
- Clients are supposed to use the FCPClientReferenceImplementation which is tested by DebugFCPClient, so the removed code is of little relevance to them as well. It would be good to allow clients to request synchronization at arbitrary times by an FCP message though in case they want to implement their own client. Bug filed: https://bugs.freenetproject.org/view.php?id=6103