Correct Dave, Eve, and Ferdie to not run as validators

substrate/tendermint/client/src/block_import.rs

@@ -19,6 +19,8 @@ impl<T: TendermintValidator> TendermintImport<T> {
     // If it's in chain, with justifications, return it's already on chain
     // If it's in chain, without justifications, continue the block import process to import its
     // justifications
+    // This can be triggered if the validators add a block, without justifications, yet the p2p
+    // process then broadcasts it with its justifications
     if (self.client.status(id).unwrap() == BlockStatus::InChain) &&
       self.client.justifications(&id).unwrap().is_some()
     {