xfs: various operations on mounted fs

xfs: various operations on mounted fs

xfsprogs takes use of ustat(2) to check if a given device is
mounted, but ustat(2) is deprecated and may not be available on
newer architectures, e.g. aarch64. In such cases, xfsprogs failed to
detect mounted device, which would result in something like
xfs_mdrestore overwriting a mounted XFS.

So adding a case to do xfs_mdrestore, xfs_copy, xfs_db, mkfs and
xfs_repair against mounted XFS to make sure they refuse to do so.

Signed-off-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>