eng_devcrypto: close session on cleanup, not final

Close the session in digest_cleanup instead of digest_final.  A failure
in closing the session does not mean a previous successful digest final
has failed as well.

Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7585)