Fix AbstractSimpleEngineTests versioning tests.

Version is now stored on a distinct field, that AbstractSimpleEngineTests
didn't correctly add before running tests. This generated a test failure
when the version needed to be loaded from the index.

src/test/java/org/elasticsearch/test/unit/index/engine/AbstractSimpleEngineTests.java

@@ -129,6 +129,7 @@ public abstract class AbstractSimpleEngineTests {
         Field uidField = new Field("_uid", uid, UidFieldMapper.Defaults.FIELD_TYPE);
         Field versionField = new NumericDocValuesField("_version", 0);
         document.add(uidField);
+        document.add(versionField);
         return new ParsedDocument(uidField, versionField, id, type, routing, timestamp, ttl, Arrays.asList(document), analyzer, source, mappingsModified);
     }