[LTP] [PATCH v2] listmount04: Detect EBADF behavior dynamically at runtime

[Wake Liu]

Hi Petr,

Gentle ping on this v2 patch.

All comments from v1 have been addressed (renamed macros back to
BEFORE_6_18/AFTER_6_18 and removed the unnecessary ENOSYS check).

Could you please take a look when you have time?

Thanks,
Wake