Use ensure_packages with dnsmasq package resource

Use ensure_packages with the dnsmasq package resource to allow
coexistance with other modules which define the same resource
name (puppet-cobbler, for example).

Cherry-pick from review.openstack.org/#/c/61737/

Change-Id: I4fb081f822596f2f025f952525d5333c5a5b1364
Merge remote-tracking branch 'remotes/origin/stable/havana' into havana