Support GPGME_ENCRYPT_ALWAYS_TRUST also for S/MIME.

* src/engine-gpgsm.c (gpgsm_encrypt): Send the always-trust options.
* tests/run-encrypt.c: Add option --always-trust.

Note that the run-encrypt test tool used to assume always-trust for
OpenPGP since 1.7.0 This bug has also been fixed by introducing the
explicit option.

• GnuPG-bug-id: T6559