PEP8 cleanup for node/market.py through node/openbazaar.py

Minor PEP8 clean up commit 2 of 3.
The old version is bad but the new version looks confusing; one has to know that python wraps lines inside `{ ... }` to understand the `if`s are actually inline. I know there is no need for such delicate treating of `nat_status`, so go ahead and write:
```python
{
    "nat_status" = self.nat_status,
    "server_public_ip": self.server_public_ip
...
}
```