Change cms_sign_data to use sha256 message digest

cms_sign_data was not passing the md parameter to openssl, so it was
using the default digest of sha1. Some security standards require a
SHA2 algorithm for the digest.

This if for security hardening.

SecurityImpact

Change-Id: Iff063149e1f12df69bbf9015222d09d798980872
Closes-Bug: #1362343
Merge "Change cms_sign_data to use sha256 message digest"