Ensure_resource on dnsmasq package

As dnsmasq is sometimes required by other modules,
in particular ones that are not in puppet-openstack,
this can cause duplicate declaration issues. By
using ensure_resource, we can avoid these problems
and both modules can declare the package.

Backport of I32f29bcac3cf67a2644b3e5eb50621f8e27b1cb1

Change-Id: Id7c66c20b62890df51c37f608087234a5b470eae