python3: fix reraise

Related to six bug https://bitbucket.org/gutworth/six/issue/86/sixreraise-exception_object-none-traceback

closes: https://github.com/vmware/pyvmomi/issues/92
python3: fix cookie handler in test

* tries both cases for the set-cookie header to make sure we catch cookie transitions.
* tampers with basic_connection fixture to demonstrate

closes: https://github.com/vmware/pyvmomi/issues/93
Merge pull request #94 from hartsock/python3

Python3: fix cookie handler in test & reraise exception handler