RabbitMQ clustering fix for v4.1.2

Addresses issue with Erlang cookie in RabbitMQ clustering by
preseeding the /var/lib/rabbitmq/.erlang.cookie file with the
default value from the cookbooks.

This could be handled in a number of different ways, but this is
the simplest way and takes care of it before the Chef environment
is created.
Set permissions on Erlang cookie for CentOS

The RHEL packages for rabbitmq-server don't fix the permissions
and ownership on the .erlang.cookie like Ubuntu does. Because of
this, we're manually changing the ownership to rabbitmq and perms
to 0400.
Merge pull request #16 from rsoprivatecloud/rabbitmq-cluster-fix

Merge fixes for RabbitMQ clustering