apache: clean up init.pp & params.pp

* Remove all the RedHat/EC2-specific configurations & logic
* Replace variable package, service and vhost dirs with their literal value on
  Debian-based systems.
* Keep the resource names the same for now, so references to Package['httpd'] /
  Service['httpd'] continue working as before.

Change-Id: I419abaf4d48bfef0c5c66e3ee4b518bb7ef9e51c