Reinit Hub when using old version of gevent.
Reinit Hub when using old version of gevent.

fix #654

z-fork/gunicorn,gtrdotmcs/gunicorn,ccl0326/gunicorn,prezi/gunicorn,malept/gunicorn,prezi/gunicorn,GitHublong/gunicorn,wong2/gunicorn,tempbottle/gunicorn,zhoucen/gunicorn,jamesblunt/gunicorn,jamesblunt/gunicorn,WSDC-NITWarangal/gunicorn,prezi/gunicorn,jamesblunt/gunicorn,zhoucen/gunicorn,gtrdotmcs/gunicorn,1stvamp/gunicorn,1stvamp/gunicorn,mvaled/gunicorn,beni55/gunicorn,malept/gunicorn,gtrdotmcs/gunicorn,mvaled/gunicorn,mvaled/gunicorn,malept/gunicorn,ephes/gunicorn,wong2/gunicorn,wong2/gunicorn,tejasmanohar/gunicorn,ccl0326/gunicorn,keakon/gunicorn,zhoucen/gunicorn,1stvamp/gunicorn,harrisonfeng/gunicorn,ccl0326/gunicorn,MrKiven/gunicorn,elelianghh/gunicorn