iolog: account for wasted time in ipo stall

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/fio.h b/fio.h
index 0601b37..5e352c6 100644
--- a/fio.h
+++ b/fio.h
@@ -252,6 +252,7 @@
 	struct timeval start;	/* start of this loop */
 	struct timeval epoch;	/* time job was started */
 	struct timeval last_issue;
+	long time_offset;
 	struct timeval tv_cache;
 	struct timeval terminate_time;
 	unsigned int tv_cache_nr;