iplb: Be tolerant of reconnections
iplb: Be tolerant of reconnections

Previously, if a switch disconnected, the load balancer would stop working
until POX was restarted.  This fixes that, though it's a bit ugly.

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