openflow/of_01.py: fix warning with DummyOFNexus
openflow/of_01.py: fix warning with DummyOFNexus

VamsikrishnaNallabothu/pox,noxrepo/pox,kavitshah8/SDNDeveloper,noxrepo/pox,MurphyMc/pox,xAKLx/pox,andiwundsam/_of_normalize,kulawczukmarcin/mypox,PrincetonUniversity/pox,chenyuntc/pox,VamsikrishnaNallabothu/pox,andiwundsam/_of_normalize,denovogroup/pox,waltznetworks/pox,kavitshah8/SDNDeveloper,carlye566/IoT-POX,carlye566/IoT-POX,diogommartins/pox,diogommartins/pox,kulawczukmarcin/mypox,xAKLx/pox,kpengboy/pox-exercise,denovogroup/pox,xAKLx/pox,MurphyMc/pox,andiwundsam/_of_normalize,MurphyMc/pox,noxrepo/pox,kpengboy/pox-exercise,VamsikrishnaNallabothu/pox,kulawczukmarcin/mypox,adusia/pox,diogommartins/pox,waltznetworks/pox,kulawczukmarcin/mypox,kavitshah8/SDNDeveloper,xAKLx/pox,jacobq/csci5221-viro-project,kulawczukmarcin/mypox,jacobq/csci5221-viro-project,pthien92/sdn,carlye566/IoT-POX,MurphyMc/pox,kpengboy/pox-exercise,pthien92/sdn,pthien92/sdn,diogommartins/pox,denovogroup/pox,PrincetonUniversity/pox,kpengboy/pox-exercise,denovogroup/pox,waltznetworks/pox,kavitshah8/SDNDeveloper,jacobq/csci5221-viro-project,xAKLx/pox,kpengboy/pox-exercise,jacobq/csci5221-viro-project,pthien92/sdn,carlye566/IoT-POX,chenyuntc/pox,MurphyMc/pox,adusia/pox,chenyuntc/pox,noxrepo/pox,adusia/pox,VamsikrishnaNallabothu/pox,adusia/pox,carlye566/IoT-POX,jacobq/csci5221-viro-project,VamsikrishnaNallabothu/pox,denovogroup/pox,chenyuntc/pox,waltznetworks/pox,chenyuntc/pox,PrincetonUniversity/pox,PrincetonUniversity/pox,andiwundsam/_of_normalize,pthien92/sdn,diogommartins/pox,adusia/pox,PrincetonUniversity/pox,waltznetworks/pox