Make the digest algorithm configurable and default to SHA2 under FIPS-mode.
Make the digest algorithm configurable and default to SHA2 under FIPS-mode.

Signed-off-by: Noah Kantrowitz <1db01d43e08596f43a65fb393d969b98ee5b4dc6@coderanger.net>
mattray/ohai,chef/ohai,chef/ohai,jaymzh/ohai,higanworks/ohai,higanworks/ohai,jaymzh/ohai,mattray/ohai