nilfs2: call nilfs2_write_super from nilfs2_sync_fs

The call to ->write_super from __sync_filesystem will go away, so make
sure nilfs2 performs the same actions from inside ->sync_fs.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/nilfs2/super.c

@@ -391,6 +391,8 @@ static int nilfs_sync_fs(struct super_block *sb, int wait)
 {
 	int err = 0;
 
+	nilfs_write_super(sb);
+
 	/* This function is called when super block should be written back */
 	if (wait)
 		err = nilfs_construct_segment(sb);