Fix MultiSigner, simplify tests (#2033)

* Fix MultiSigner, use `into_signed_tx`

* Rebuild.

substrate/core/client/src/genesis.rs

@@ -46,7 +46,7 @@ mod tests {
 	use state_machine::backend::InMemory;
 	use test_client::{
 		runtime::genesismap::{GenesisConfig, additional_storage_with_genesis},
-		runtime::{Hash, Transfer, Block, BlockNumber, Header, Digest, Extrinsic},
+		runtime::{Hash, Transfer, Block, BlockNumber, Header, Digest},
 		AccountKeyring, AuthorityKeyring
 	};
 	use runtime_primitives::traits::BlakeTwo256;
@@ -68,12 +68,7 @@ mod tests {
 	) -> (Vec<u8>, Hash) {
 		use trie::ordered_trie_root;
 
-		let transactions = txs.into_iter().map(|tx| {
-			let signature = AccountKeyring::from_public(&tx.from).unwrap()
-				.sign(&tx.encode()).into();
-
-			Extrinsic::Transfer(tx, signature)
-		}).collect::<Vec<_>>();
+		let transactions = txs.into_iter().map(|tx| tx.into_signed_tx()).collect::<Vec<_>>();
 
 		let extrinsics_root = ordered_trie_root::<Blake2Hasher, _, _>(transactions.iter().map(Encode::encode)).into();