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

Minor PEP8 clean up commit 2 of 3.
This can be simplified. First of all, when a `%s` string format operator is used, Python will [automatically](https://docs.python.org/2/library/stdtypes.html#string-formatting-operations) format any arguments via `str()`, so no need to do so explicitly. Please also shorten the string so that the backslash can be removed:
```python
print "UPnP TCP P2P Port Map configuration (%s -> %s): %s" % (
    p2p_port, p2p_port, result_tcp_p2p_mapping
)
```
Again, you can place the closing `)` wherever you like.
Please simplify the UDP case below, too.