Puppet3 compatibility

Erlang needs HOME to be set so it can write a cookie to it. Since puppet3 wipes HOME for all provider commands by default, this patch reintroduces HOME for all provider commands.

This code was not written by me, but since otherwise the rabbitmq module is totally useless for puppet3 you might want to take a look at this patch, taken from: https://github.com/proventa/puppetlabs-rabbitmq