Improve socket_closed test
Improve socket_closed test

ShaneHarvey/mongo-python-driver,ShaneHarvey/mongo-python-driver,aherlihy/mongo-python-driver,WingGao/mongo-python-driver,aherlihy/mongo-python-driver,ShaneHarvey/mongo-python-driver,pigate/mongo-python-driver,mongodb/mongo-python-driver,pigate/mongo-python-driver,develf/mongo-python-driver,mongodb/mongo-python-driver,ramnes/mongo-python-driver,ramnes/mongo-python-driver,aherlihy/mongo-python-driver,mongodb/mongo-python-driver,WingGao/mongo-python-driver,ramnes/mongo-python-driver,felixonmars/mongo-python-driver,felixonmars/mongo-python-driver,develf/mongo-python-driver