Added an attribute to override the mongos port.

As defined in attributes:

```
default[:mongodb][:mongos][:port]       = 27017
default[:mongodb][:configsvr][:port]    = 27019
```

[ticket: X]: ?
Names of services now include a mongodb as prefix
Support to override the mongos port and list of config servers.

[ticket: X]: ?
Adding a comment that ref the template file