Investigate two test issues:

1. Occasional deadlocks in PyPy and PyPy3:

https://jenkins.10gen.com/view/Python/job/mongo-python-driver/234/extensions=without-extensions,label=linux64,mongodb_configuration=replica_set,mongodb_option=noauth,mongodb_server=master-nightly,python_language_version=pypy/console

https://jenkins.10gen.com/view/Python/job/mongo-python-driver/228/extensions=without-extensions,label=linux64,mongodb_configuration=replica_set,mongodb_option=noauth,mongodb_server=30-release,python_language_version=pypy3/console

2. "Cannot join thread before it is started" during PyPy3 interpreter shutdown.

https://jenkins.10gen.com/view/Python/job/mongo-python-driver/extensions=without-extensions,label=linux64,mongodb_configuration=replica_set,mongodb_option=noauth,mongodb_server=master-nightly,python_language_version=pypy3/236/console