Improve Security practices

[arm4b]

From the:

• Use safer default values st2-packages#405
• Add some security best practices notes to the docs st2docs#363

At the moment we don't even configure any username/passwords for external services like Mongo, RabbitMQ with st2 Ansible installation. Additionally, we're not sure whether those services are listening on 127.0.0.1 or are open to public net.

All of that needs better control and improvement.

• Ensure we can configure host for dependent services
• Services should run on 127.0.0.1 (PostgreSQL, Mongo, RabbitMQ) by default
• Configure/Set username/password for PostgreSQL, Mongo, RabbitMQ
• If not explicitly set, passwords for PostgreSQL, Mongo, RabbitMQ should be generated randomly and placed in st2.conf

[cognifloyd]

Here's a gist of some tasks that will idempotently (or at least I think they're idempotent):

• Turn on authorization in mongo, add admin user, and add st2 user
• Add rabbitmq management plugin, remove guest user and add a rabbitmq user for stackstorm

There's also a set of group_vars for my stackstorm group in my inventory.

https://gist.github.com/cognifloyd/c03cafc62f26a3ea0cfe1a5ed5c4238d

[cognifloyd]

#162 for mongo and #164 for rabbitmq