Content sources container download implemented using queues.
Merge branch 'master' into jortel-US2888-CS
Removed total_passes from content sources download report.
docstrings.
use 'with self._mutex; docstring fixes.
Merge branch 'master' into jortel-US2888-CS
next() reimplemented.
in-progress tracker.
pep8.
Merge pull request #1079 from pulp/jortel-US2888-CS

Content sources container download implemented using queues.