overlay/036: fix upper/lower dir mismatch

overlay/036: fix upper/lower dir mismatch

Mount option index=on checks on mount that upper dir is not being
reused with a different lower dir than the first lower dir it was
mounted with. This behavior is verified by test overlay/037.

In this test however, it is not desired to fail mount on mismatch of
upper/lower, so use the matching upper/lower dirs in this test.

The mismatch went unnoticed because the index=off mounts do not
verify lower dir and the index=on mounts fails on EBUSY (dir in use
by another live mount) before failing on ESTALE (upper/lower dir
mismatch).

Never the less, fix the mismatch, so a change in the kernel between
the two sanity checks (EBUSY vs. ESTALE) won't break the test.

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