Use $package variable in package resource when using httpfile

In my previous fix for the `package` resource name I missed the `package` when using `httpfile`. I am actually using Riak EE and using our custom provided package and it was failing. This should fix that scenario.

Note: There were already two unit tests failing and I am not sure how to fix them yet:

```
Failures:

  1) riak::vmargs at baseline defaults
     Failure/Error: }) }
     Puppet::Error:
       Duplicate declaration: Class[Riak::Vmargs] is already declared; cannot redeclare at /Users/ashinn/Projects/puppet-riak/spec/fixtures/modules/riak/manifests/init.pp:225 on node andys-macbook.local
     # ./spec/classes/vmargs_spec.rb:18:in `block (3 levels) in <top (required)>'

  2) riak::vmargs when decommissioning w/ params (absent):
     Failure/Error: it { should contain_file('/etc/riak/vm.args').with_ensure('absent') }
     Puppet::Error:
       Duplicate declaration: Class[Riak::Vmargs] is already declared; cannot redeclare at /Users/ashinn/Projects/puppet-riak/spec/fixtures/modules/riak/manifests/init.pp:225 on node andys-macbook.local
     # ./spec/classes/vmargs_spec.rb:35:in `block (3 levels) in <top (required)>'
```

But I did update the test for the `riak` class custom package name.