nilfs2: fix problem in setting checkpoint interval

Checkpoint generation interval of nilfs goes wrong after user has
changed the interval parameter with nilfs-tune tool.

 segctord starting. Construction interval = 5 seconds,
 CP frequency < 30 seconds
 segctord starting. Construction interval = 0 seconds,
 CP frequency < 30 seconds

This turned out to be caused by a trivial bug in initialization code
of log writer.  This will fix it.
Reported-by: NAndrea Gelmini <andrea.gelmini@gmail.com>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

fs/nilfs2/segment.c

@@ -2573,7 +2573,7 @@ static struct nilfs_sc_info *nilfs_segctor_new(struct super_block *sb,
 	sci->sc_watermark = NILFS_SC_DEFAULT_WATERMARK;
 
 	if (nilfs->ns_interval)
-		sci->sc_interval = nilfs->ns_interval;
+		sci->sc_interval = HZ * nilfs->ns_interval;
 	if (nilfs->ns_watermark)
 		sci->sc_watermark = nilfs->ns_watermark;
 	return sci;