dns/py-py3dns: Limit to Python 3.x, Fix dependencies

[koobs]

Summary

Commit log:

dns/py-py3dns: Limit to Python 3.x, Fix dependencies

py-py3dns is a Python 3.x only package, so limit USES=python
accordingly. ipaddr is needed on <= 3.2, so add it as a conditional
RUN_DEPENDS.

While I'm here:

- Add NO_ARCH
- Add test target, TEST_DEPENDS and patch outdated unit test assertions
  that test against live domains, not mocked responses.
- Remove unnecessary setup.py patch
- Match COMMENT to setup.py:description
- Sort and group USE{S} entries

PR:		206645
Reported by:	danger
Approved by:	portmgr (blanket)
MFH:		2016Q1
DiffRev:	D5083

Test Plan

• portlint: OK (looks fine.)
• testport: OK (poudriere: 11amd64, python34)
• unittest: OK (20 passed in 5.60 seconds)