eng_devcrypto: close open session on init

cipher_init may be called on an already initialized context, without a
necessary cleanup.  This separates cleanup from initialization, closing
an eventual open session before creating a new one.

Move the /dev/crypto session cleanup code to its own function.

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

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/8306)