Provide for uninstalling docker and deps, rm init.d script ONLY for ubuntu (with upstart)

I have successfully tested the uninstall functionality (by setting $docker::params::ensure to 'purged').  These changes will purge, or supposedly absent docker (and its dependent packages).  Restoring the ::ensure value to 'present' restores the installation successfully.  I made no attempt to remove the /etc/apt/sources.list.d/docker.list file nor to purge the apt key.  

I failed to find an init.d script upon reinstall.  I am unsure whether that means that no such script exists in the package, or if my conditional wrapper has a bug in it.  I will investigate that further after lunch, perhaps.  Still need to sort out how to start the docker service on a debian server.