Enable most unit tests for py34 job

Enable most unit tests for py34 job

* Skip TestWSGIServerWithSSL[1] for Python 3 since it seems wsgi + ssl +
  eventlet setup does not behave correctly now,
* Skip test_json_with_utf8[2] until we solve unicode/utf8 encode/decode,
* Fix some more tests to pass for py3,
* Replace print by print() in docs/docstrings.

[1] neutron.tests.unit.test_wsgi (bug 1482633)
[2] neutron.tests.unit.test_wsgi.JSONDictSerializerTest (bug 1491824)

Related-Bug: #1482633
Related-Bug: #1491824
Blueprint: neutron-python3
Co-Authored-By: Cyril Roelandt <cyril@redhat.com>
Co-Authored-By: Cedric Brandily <zzelle@gmail.com>
Co-Authored-By: sonu.kumar <sonu.kumar@nectechnologies.in>
Change-Id: I26e513d4dcf473f4cd79728382fc94af3d901b5d