Fix a possible memory leak in sxnet_v2i

Fix a possible memory leak in sxnet_v2i

When a subsequent call to SXNET_add_id_asc fails
e.g. because user is a string larger than 64 char
or the zone is a duplicate zone id,
or the zone is not an integer,
a memory leak may be the result.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23234)