fix datapath disconnection cleanup
fix datapath disconnection cleanup

After the datapath connection is close, we call gevent.joinall for
ev_thr and send_thr greenlets to wait for the completion of them.
However, gevent.joinall will block forever since the greenlets sleep.
We can put some junk to the queues to wake them but looks like just
killing the greenlets is simpler.

Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

jalilm/ryu,shinpeimuraoka/ryu,alyosha1879/ryu,habibiefaried/ryu,unifycore/ryu,citrix-openstack/build-ryu,haniehrajabi/ryu,zangree/ryu,muzixing/ryu,o3project/ryu-oe,lsqtongxin/ryu,fujita/ryu,haniehrajabi/ryu,sivaramakrishnansr/ryu,pichuang/ryu,evanscottgray/ryu,ttsubo/ryu,habibiefaried/ryu,Tesi-Luca-Davide/ryu,iwaseyusuke/ryu,Tejas-Subramanya/RYU_MEC,hisaharu/ryu,hisaharu/ryu,castroflavio/ryu,fujita/ryu,umkcdcrg01/ryu_openflow,OpenState-SDN/ryu,fujita/ryu,Zouyiran/ryu,openvapour/ryu,alanquillin/ryu,zangree/ryu,evanscottgray/ryu,John-Lin/ryu,gopchandani/ryu,ttsubo/ryu,lagopus/ryu-lagopus-ext,hisaharu/ryu,yamt/ryu,Tesi-Luca-Davide/ryu,yamada-h/ryu,lagopus/ryu-lagopus-ext,Tejas-Subramanya/RYU_MEC,ntts-clo/mld-ryu,jkoelker/ryu,darjus-amzn/ryu,lagopus/ryu-lagopus-ext,takahashiminoru/ryu,Tejas-Subramanya/RYU_MEC,openvapour/ryu,StephenKing/ryu,ntts-clo/ryu,alanquillin/ryu,TakeshiTseng/ryu,gopchandani/ryu,lsqtongxin/ryu,mikhaelharswanto/ryu,takahashiminoru/ryu,fkakuma/ryu,fujita/ryu,shinpeimuraoka/ryu,Zouyiran/ryu,osrg/ryu,jalilm/ryu,diogommartins/ryu,iwaseyusuke/ryu,torufuru/OFPatchPanel,TakeshiTseng/ryu,samrussell/ryu,fkakuma/ryu,osrg/ryu,gareging/SDN_Framework,torufuru/oolhackathon,muzixing/ryu,gopchandani/ryu,alanquillin/ryu,takahashiminoru/ryu,citrix-openstack-build/ryu,yamt/ryu,alyosha1879/ryu,StephenKing/ryu,o3project/ryu-oe,hisaharu/ryu,gareging/SDN_Framework,muzixing/ryu,unifycore/ryu,lagopus/ryu-lagopus-ext,StephenKing/ryu,sivaramakrishnansr/ryu,ykaneko/ryu,umkcdcrg01/ryu_openflow,umkcdcrg01/ryu_openflow,Tesi-Luca-Davide/ryu,alyosha1879/ryu,evanscottgray/ryu,StephenKing/ryu,elahejalalpour/ELRyu,John-Lin/ryu,torufuru/oolhackathon,ntts-clo/mld-ryu,jalilm/ryu,sivaramakrishnansr/ryu,darjus-amzn/ryu,darjus-amzn/ryu,lagopus/ryu-lagopus-ext,diogommartins/ryu,ykaneko/ryu,OpenState-SDN/ryu,hisaharu/ryu,ysywh/ryu,yamada-h/ryu,gopchandani/ryu,darjus-amzn/ryu,ynkjm/ryu,ynkjm/ryu,zyq001/ryu,ynkjm/ryu,openvapour/ryu,ttsubo/ryu,ysywh/ryu,openvapour/ryu,samrussell/ryu,StephenKing/summerschool-2015-ryu,shinpeimuraoka/ryu,lzppp/mylearning,pichuang/ryu,takahashiminoru/ryu,takahashiminoru/ryu,castroflavio/ryu,diogommartins/ryu,ysywh/ryu,ttsubo/ryu,lzppp/mylearning,pichuang/ryu,habibiefaried/ryu,pichuang/ryu,jalilm/ryu,haniehrajabi/ryu,jkoelker/ryu,sivaramakrishnansr/ryu,TakeshiTseng/ryu,ynkjm/ryu,jazzmes/ryu,diogommartins/ryu,TakeshiTseng/ryu,zangree/ryu,diogommartins/ryu,John-Lin/ryu,elahejalalpour/ELRyu,yamt/ryu,lzppp/mylearning,OpenState-SDN/ryu,John-Lin/ryu,alyosha1879/ryu,zyq001/ryu,iwaseyusuke/ryu,StephenKing/summerschool-2015-ryu,gareging/SDN_Framework,zangree/ryu,ysywh/ryu,elahejalalpour/ELRyu,gareging/SDN_Framework,lzppp/mylearning,torufuru/oolhackathon,StephenKing/ryu,osrg/ryu,StephenKing/summerschool-2015-ryu,gareging/SDN_Framework,ttsubo/ryu,iwaseyusuke/ryu,shinpeimuraoka/ryu,openvapour/ryu,mikhaelharswanto/ryu,Tesi-Luca-Davide/ryu,John-Lin/ryu,fkakuma/ryu,alanquillin/ryu,zyq001/ryu,darjus-amzn/ryu,elahejalalpour/ELRyu,jalilm/ryu,umkcdcrg01/ryu_openflow,gopchandani/ryu,sivaramakrishnansr/ryu,alanquillin/ryu,muzixing/ryu,lsqtongxin/ryu,iwaseyusuke/ryu,StephenKing/summerschool-2015-ryu,haniehrajabi/ryu,Zouyiran/ryu,jkoelker/ryu,fkakuma/ryu,ynkjm/ryu,Tejas-Subramanya/RYU_MEC,haniehrajabi/ryu,elahejalalpour/ELRyu,osrg/ryu,citrix-openstack-build/ryu,Tejas-Subramanya/RYU_MEC,muzixing/ryu,ysywh/ryu,shinpeimuraoka/ryu,lsqtongxin/ryu,Zouyiran/ryu,zyq001/ryu,jazzmes/ryu,ntts-clo/ryu,zyq001/ryu,yamt/ryu,lzppp/mylearning,fkakuma/ryu,pichuang/ryu,habibiefaried/ryu,jazzmes/ryu,OpenState-SDN/ryu,fujita/ryu,castroflavio/ryu,lsqtongxin/ryu,StephenKing/summerschool-2015-ryu,osrg/ryu,torufuru/OFPatchPanel,umkcdcrg01/ryu_openflow,habibiefaried/ryu,Zouyiran/ryu,Tesi-Luca-Davide/ryu,TakeshiTseng/ryu,OpenState-SDN/ryu,zangree/ryu,yamt/ryu,citrix-openstack/build-ryu