gevent: don't confound socket timeout with zero read
gevent: don't confound socket timeout with zero read

PYTHON-573

datastax/python-driver,thelastpickle/python-driver,kishkaru/python-driver,vipjml/python-driver,stef1927/python-driver,mambocab/python-driver,vipjml/python-driver,kishkaru/python-driver,mambocab/python-driver,datastax/python-driver,stef1927/python-driver,coldeasy/python-driver,coldeasy/python-driver,thobbs/python-driver,thelastpickle/python-driver,thobbs/python-driver