BUG/MEDIUM: hlua_fcn: ensure systematic bref cleanup for patref list iterator

BUG/MEDIUM: hlua_fcn: ensure systematic bref cleanup for patref list iterator

Similar bug as aeff2a3b2a ("BUG/MEDIUM: hlua_fcn: ensure systematic watcher
cleanup for server list iterator") but this time it affects patref list
iterator.

If the patref list iteration is interrupted (ie: break away from the loop
or lua error), we still need to unlink the bref we set earlier because
the hlua_patref_iterator_context is a temporary object so we cannot
let a reference once the object is dead. Obviously this can corrupt
the pattern reference element bref "users" list and lead to invalid
reads as well.

Reported-by: Claude (ANT-2026-DARC9AY8)
It should be backported up to 3.2 where hlua patref API was implemented.