Btrfs: update inode ctime when using links

Currently we fail xfstest 236 because we're not updating the inode ctime on
link.  This is a simple fix, and makes it so we pass 236 now.

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/inode.c

@@ -4785,6 +4785,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
 		return -EPERM;
 
 	btrfs_inc_nlink(inode);
+	inode->i_ctime = CURRENT_TIME;
 
 	err = btrfs_set_inode_index(dir, &index);
 	if (err)