Adds fail2ban filter and jail configs

The values used in prod will be defined at runtime so replacing them
with default values

Closes rc/hpc-factory#173

Closes rc/hpc-factory#175

Now as a dictionary that includes:
- src: mount source
- path: mount path
- opts: mount options

- Ensure the `/tmp/ssh_keys` directory exists.
- Download SSH host keys from S3 and unpack them to `/etc/ssh`.
- Restart the SSH service to apply the new keys.
- Add necessary variables for S3 and AWS credentials in `groupvars/all`.
- Include `ssh_host_keys` role in `cluster.yml` playbook.

We parameterized a few tasks in the cheaha.yml and put the vars in
group_vars/all so that the existing knightly builds won't break.
We added values required for the CoD deploy in group_vars/proxy. Now if
we put the proxy nodes in proxy group they will inherit values meant for
CoD deploy which is not desired in production.
We later realized that the appropriate file is group_vars/knightly and
it gives flexibility to put proxy nodes in knightly group to override
the vars meant for CoD in group_vars/all.

This will enable a standalone VM to interact with cluster so it can act
as a proxy for services. eg. OOD,SSH etc.