Revert "logical error in decode()"

This needs to be reverted because it breaks all the other codepaths since it
just doesn't return anything on read or scan.

This reverts commit 44660de7.

couchbase2/src/main/java/com/yahoo/ycsb/db/couchbase2/Couchbase2Client.java

@@ -856,7 +856,7 @@ public class Couchbase2Client extends DB {
       for (Iterator<Map.Entry<String, JsonNode>> jsonFields = json.fields(); jsonFields.hasNext();) {
         Map.Entry<String, JsonNode> jsonField = jsonFields.next();
         String name = jsonField.getKey();
-        if (!(checkFields && fields.contains(name))) {
+        if (checkFields && fields.contains(name)) {
           continue;
         }
         JsonNode jsonValue = jsonField.getValue();