xfs: fix xfs_quota remove error

The xfs_quota returns ENOSYS when remove command is executed.
Reproducable with following steps.

    # mount -t xfs -o uquota /dev/sda7 /mnt/mp1
    # xfs_quota -x -c off -c remove
    XFS_QUOTARM: Function not implemented.

The remove command is allowed during quotaoff, but xfs_fs_set_xstate()
checks whether quota is running, and it leads to ENOSYS.

To solve this problem, add a check for X_QUOTARM.

Signed-off-by: Ryota Yamauchi <r-yamauchi@vf.jp.nec.com>
Signed-off-by: Utako Kusaka <u-kusaka@wm.jp.nec.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

fs/xfs/linux-2.6/xfs_quotaops.c

@@ -80,7 +80,7 @@ xfs_fs_set_xstate(
 
 	if (sb->s_flags & MS_RDONLY)
 		return -EROFS;
-	if (!XFS_IS_QUOTA_RUNNING(mp))
+	if (op != Q_XQUOTARM && !XFS_IS_QUOTA_RUNNING(mp))
 		return -ENOSYS;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;