Update apache::params for Amazon Linux

Amazon Linux AMI is a lot like RedHat 6 but has an
`$operatingsystemrelease` value of `3.4.37-40.44.amzn1.x86_64`
currently which throws off the `$distrelease` in the params class.

Adding these defaults should fix this issue.
Merge pull request #288 from hunner/update_amazon

Update apache::params for Amazon Linux