SSH service name based on distro, Ubuntu ssh upstart issue, repeated keyword on ssh_config

This fixes 4 separate issues:

1. **Cookbook name:** Added to `metadata.rb` for compatibility
2. **SSH service name:** support changing service name based on distro (issue #4)
3. **[COOK-3910](https://tickets.opscode.com/browse/COOK-3910):** Uses `Chef::Provider::Service::Upstart` provider when restarting the service on Ubuntu 13 and up
4. **Duplicated keywords:** If `sshd_config` has duplicated keywords (say with #commented out) the sed command will replace both, often causing ssh to break.

This is an example I ran into for item 4:

Original sshd_config file
```
#UseDNS yes
UseDNS no
```

Modified after Ched run
```
UseDNS no
UseDNS no
```