xfs: test xfsdump with bind-mounted filesystem

xfs: test xfsdump with bind-mounted filesystem

commit 25195eb ("xfsdump: handle bind mount target") introduced
a bug of xfsdump which doesn't store the files to the dump file
correctly when the root inode number is changed.

The commit 25195eb is reverted, and commit 0717c1c ("xfsdump: intercept
bind mount targets") which is in xfsdump v3.1.10 fixes the bug to reject
the filesystem if it's bind-mounted.

Test that xfsdump can reject the bind-mounted filesystem.

Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>