Fix problem with f->last_completed_pos not being correct on requeues

This causes an unnecessary seek. Usually this is just noise, but if
the device isn't seekable, it becomes a real problem.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 7ac5734..9c398a2 100644
--- a/fio.h
+++ b/fio.h
@@ -135,6 +135,7 @@
 	void *buf;
 	unsigned long buflen;
 	unsigned long long offset;
+	unsigned long long endpos;
 
 	/*
 	 * IO engine state, may be different from above when we get