fix oom cause missing data bug (#163)

Signed-off-by: marsishandsome <marsishandsome@gmail.com>

src/main/java/org/tikv/common/operation/iterator/DAGIterator.java

@@ -224,7 +224,6 @@ public abstract class DAGIterator<T>
                 + " tasks not executed due to",
             e);
         // Rethrow to upper levels
-        eof = true;
         throw new RegionTaskException("Handle region task failed:", e);
       }
     }