datapaths: Allow table_id to be 0
datapaths: Allow table_id to be 0

flow/aggregate stats requests were requiring that the table specified
be TABLE_ALL, but 0 should also be allowed.

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