Add XCCDF Value sshd_required to other products

[yuumasato]

Description:

• Add Value sshd_required to products that implement their own SSH Rules.
• Edit OVAL check for Rule disable_host_auth to use Value sshd_required.

Rationale:

#2272 introduced Value sshd_required for SSH Rules in Shared.
But some products don't gather XCCDF Rules for SSH from shared, they have their own Rules in their own directories, these products are:

• Fedora
• RHEL6
• Debian 8
• Ubuntu 14 and 16

Although, these products have their own Rules for SSH, they still rely on OVAL checks from shared.
So the Rules need to define Value sshd_required.

• Fixes SSH rules broken in common Fedora profile #2426

[jan-cerny]

Thank you for fixing this, it looks good to me.