[NC-1752] Fix SSTORE original value (#79)

* [NC-1752] Delegate calls to getOriginalAccount all the way to the actual store. Ensures we get the actual original value even when updaters are nested due to nested calls.

* Upgrade ethereum reference tests to include the new sstore tests.
Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/AbstractWorldUpdater.java

@@ -79,7 +79,7 @@ public abstract class AbstractWorldUpdater<W extends WorldView, A extends Accoun
 
   @Override
   public Account getOriginalAccount(final Address address) {
-    return world.get(address);
+    return world.getOriginalAccount(address);
   }
 
   @Override

ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/WorldUpdater.java

@@ -77,14 +77,6 @@ public interface WorldUpdater extends MutableWorldView {
    */
   MutableAccount getMutable(Address address);
 
-  /**
-   * Retrieve the original account, prior to any modifications made by this updater.
-   *
-   * @param address the address of the account.
-   * @return the account {@code address} or {@code null} if the account does not exist.
-   */
-  Account getOriginalAccount(Address address);
-
   /**
    * Deletes the provided account.
    *

ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/WorldView.java

@@ -14,7 +14,18 @@ package tech.pegasys.pantheon.ethereum.core;
 
 /** Generic interface for a view over the accounts of the world state. */
 public interface WorldView {
-  WorldView EMPTY = address -> null;
+  WorldView EMPTY =
+      new WorldView() {
+        @Override
+        public Account get(final Address address) {
+          return null;
+        }
+
+        @Override
+        public Account getOriginalAccount(final Address address) {
+          return null;
+        }
+      };
 
   /**
    * Get an account provided it's address.
@@ -24,4 +35,12 @@ public interface WorldView {
    *     such account.
    */
   Account get(Address address);
+
+  /**
+   * Retrieve the original account, prior to any modifications made in this transaction.
+   *
+   * @param address the address of the account.
+   * @return the account {@code address} or {@code null} if the account does not exist.
+   */
+  Account getOriginalAccount(Address address);
 }

ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/worldstate/DefaultMutableWorldState.java

@@ -100,6 +100,11 @@ public class DefaultMutableWorldState implements MutableWorldState {
         .orElse(null);
   }
 
+  @Override
+  public Account getOriginalAccount(final Address address) {
+    return get(address);
+  }
+
   private AccountState deserializeAccount(
       final Address address, final Hash addressHash, final BytesValue encoded) throws RLPException {
     final RLPInput in = RLP.input(encoded);