Add 'f' (Finishing) flag to status output

Use this for finalizing logs when a thread is done, since
that can take a long time.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/HOWTO b/HOWTO
index 47eff96..7db7b89 100644
--- a/HOWTO
+++ b/HOWTO
@@ -1590,6 +1590,7 @@
 	M	Running, doing mixed sequential reads/writes.
 	m	Running, doing mixed random reads/writes.
 	F	Running, currently waiting for fsync()
+	f	Running, finishing up (writing IO logs, etc)
 	V	Running, doing verification of written data.
 E		Thread exited, not reaped by main thread yet.
 _		Thread reaped, or