Improve data direction runtime logging

If we cut a data direction short, log that time so we don't
account the full runtime.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 1fb01d9..e333490 100644
--- a/fio.h
+++ b/fio.h
@@ -493,6 +493,8 @@
 
 	struct timeval start;	/* start of this loop */
 	struct timeval epoch;	/* time job was started */
+	struct timeval rw_end[2];
+	unsigned int rw_end_set[2];
 
 	/*
 	 * read/write mixed workload state