overlay: test constant ino with nested overlay over non-samefs lower

overlay: test constant ino with nested overlay over non-samefs lower

Also test that d_ino of readdir entries and i_ino from /proc/locks are
consistent with st_ino and that inode numbers persist after rename to
new parent, drop caches and mount cycle.

With nested xino configuration, directory st_ino is not persistent and
its st_ino/d_ino/i_ino values are not consistent, so test only non-dir
in this test.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>