kdb: fix memory handling in ipadb_find_principal
BER structure representing a string might not have termination '\0'
character, thus we should use length-bound functions to operate on it.
Memory handling of LDAP values was leaving previous vals over iteration.
Also, when freeing vals, we need to explicitly set it to NULL.
Fixes: https://pagure.io/freeipa/issue/8291
Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-by: Simo Sorce <ssorce@redhat.com>
Reviewed-By: Christian Heimes <cheimes@redhat.com>