[Cook 3460] Support Amazon linux in ebs_raid LWRP

Updated update_initramfs method with a `node["platform"]` case statement that supports RHEL derivatives.  If platform is not Debian or RHEL based, throw a warning and continue on assuming that the user can manually handle the update.

I did not update the default `filesystem_options` parameter with a platform case statement even though `nobootwait` is not supported by Amazon Linux and causes `mount` to fail.  It may be a better option to simply remove `nobootwait` as a default and put a note in the README for recommended settings.