[tests] Port unittest_cwctl to py3k
On python 2, sys.stdout takes bytes-like objects whereas python 3's
takes unicode-like objects and handles the encoding on its own.
change_attribute_type('CWCache', 'timestamp', 'TZDatetime')
change_attribute_type('CWUser', 'last_login_time', 'TZDatetime')
change_attribute_type('CWSource', 'latest_retrieval', 'TZDatetime')
drop_attribute('CWSource', 'synchronizing')
add_attribute('CWSource', 'in_synchronization')