datapaths: Improve vendor errors
datapaths: Improve vendor errors

Set XID and data for errors in response to OFPT_VENDOR.

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