[3.5] bpo-29738: Fix memory leak in _get_crl_dp (GH-526) by Mariatta · Pull Request #1143 · python/cpython

* Remove conditional on free of `dps`, since `dps` is now allocated for
all versions of OpenSSL
* Remove call to `x509_check_ca` since it was only used to cache
the `crldp` field of the certificate
CRL_DIST_POINTS_free is available in all supported versions of OpenSSL
(recent 0.9.8+) and LibreSSL.
(cherry picked from commit 2849cc3)