Sync block verification (#74)

* Synchronize block verification
* max_round_blocks_to_import set to 1
* Fixed test that rely on 12block batches

Co-authored-by: adria0.eth <5526331+adria0@users.noreply.github.com>

ethcore/src/tests/client.rs

@@ -278,7 +278,7 @@ fn can_handle_long_fork() {
     push_blocks_to_client(&client, 49, 1201, 800);
     push_blocks_to_client(&client, 53, 1201, 600);
 
-    for _ in 0..400 {
+    for _ in 0..2300 {
         client.import_verified_blocks();
     }
     assert_eq!(2000, client.chain_info().best_block_number);