Avoid passing last and depth to x509_verify_cert_error() on ENOMEM.

Avoid passing last and depth to x509_verify_cert_error() on ENOMEM.

In x509_verify_ctx_set_xsc_chain(), an ENOMEM case is currently passing
the last certificate and depth (which is no longer actually depth) to
x509_verify_cert_error(). Given we've hit an ENOMEM situation, neither
of these are useful so remove both.

ok tb@