Implement firewalling in tripleo::firewall

Implement firewalling in tripleo::firewall

Currently firewalling is implemented in tripleo/init.pp this commit
moves it to its own scope tripleo/firewall.pp.

This is done so that in tripleo-heat-templates we can have a simple and
generic `include tripleo::firewall` in every manifest - unconditional.
The rest of the behavior will all be managed by hiera.

If a user wants to enable firewalling:

```
tripleo::firewall::manage_firewall: true
```

If a user wants to specify firewall rules:

```
tripleo::firewall::firewall_rules:
  '103 mongod':
    port: 27017
```

Change-Id: I144c60db2a568a94dce5b51257f1d10980173325