use {ssh.port} in creating inventory file

I need known ssh ports for each VM, when I create more then one VM on my guest.

In Vagrant::config.run I define:
```ruby
    config.ssh.port = 3330
    config.vm.forward_port  22, 3330
```
The inventory file now lists:

    [web-servers]
    127.0.0.1:2222

I am not sure if this will create problems in other configurations.