Switch all uses of urllib and HTMLParser to import from six

As part of enabling python3 support in tempest we need to be able to
handle urllib, HTMLParser, and urllib2 usage in both python2 and
python3. Six provides a compat layer for doing this, so this commit
moves all uses of urllib2, HTMLParser, and urllib to get it through
six.

Change-Id: I81e348ac79001ac94bdb92a9b60c7dca4c93686a
36 files changed