overlay/065: adjust test to expect EBUSY only with index=on

overlay/065: adjust test to expect EBUSY only with index=on

This is needed to support the kernel regression fix commit 0be0bfd2de9d
("ovl: fix regression caused by overlapping layers detection").

Overlayfs mount is not supposed to fail due to upper/work dir in-use
by other mount unless option index=on is enabled.

Add test variants for index=on and index=off.

Fix some wrong comments and clean noise lines in golden output.

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