work on unit tests (please review)

[Phil-Friderici]

starting to review the unit tests for completeness

• compress OS specific unit tests into one block per OS

finished:

• pam (mostly see comment below (and in unit tests))
• pam::accesslogin
• pam::limits
• pam::limits::fragment
• pam::service

/!\ untested functionality in pam $limits_fragments_hiera_merge $other_file $common_auth_file $common_auth_pc_file $common_account_file $common_account_pc_file $common_password_file $common_password_pc_file $common_session_file $common_session_pc_file $common_session_noninteractive_file $system_auth_file $system_auth_ac_file $password_auth_file $password_auth_ac_file $common_files $common_files_create_links $common_files_suffix

/!\ untested content validation in pam $package_name

[ghoneycutt]

I think this all got merged into the v3 branch and released. Let me know and please re-open if that's not the case.