Correctly compare values returned by 'sysctl -e -n'

You cannot directly compare the value as returned by sysctl since it typically has some extra whitespace. 

```
$sysctl -e -n net.ipv4.tcp_rmem
4096	87380	16777216
```

This commit adds a compare function which will use str.split() to compare the values disregarding whitespace. I'm not sure if my first `is None` check is required.