Invalid Justification handling

[haerdib]

With PR #365 an error will be printed upon an encountering an invalid justification instead of returning an error (and ending up in an endless loop of trying to import the block with the faulty justification , see issue #353).

However, this is only a temporary solution. Substrate handles bad justifcations alittle bit more complex: if the block enforces a justification ( needs_justification = true ) a justification is rerequest from other peers: https://github.com/paritytech/substrate/blob/master/client/finality-grandpa/src/import.rs#L642-L646

Should the worker handle this case in a similar way?

[haerdib]

Example of a block that has caused an justification error:

(copy pasted from #353 (comment))