LDAP: Use FALSE instead of bool_false when setting bits.close

bool_false is the internal name used in the setup_once.h definition
we fall back to for non-C99 non-stdbool systems, it's not the actual
name to use in assignments (we use bool_false, bool_true there to
avoid global namespace problems, see comment in setup_once.h).
The correct C99 value to use is 'false', but let's use FALSE as
used elsewhere when assigning to bits.close. FALSE is set equal
to 'false' in setup_once.h when possible.

This fixes a build problem on C99 targets.