raft: remove unused prevTerm field
raft: remove unused prevTerm field

arthurcolle/etcd,snailwalker/etcd,shawnps/etcd,westhood/etcd,CrazyJvm/etcd,etcd-io/etcd,insequent/etcd,mitake/etcd,ylong/etcd,jeremyeder/etcd,spacejam/etcd,robszumski/etcd,giantswarm/etcd,delkyd/etcd,dterei/etcd,mkumatag/etcd,bluebreezecf/etcd,junxu/etcd,siddontang/etcd,luxas/etcd,ktateish/etcd,devfreesg/etcd,sinsharat/etcd,chai2010/etcd,lumjjb/etcd,kingland/etcd,sayden/etcd,xdlinear/etcd,xychu/etcd,wfxiang08/etcd,pengzj/etcd,gae123/etcd,TheHippo/etcd,sebrandon1/etcd,Timer/etcd,xiang90/etcd,combk8s/etcd,mike-lerch/etcd,crandles/etcd,nkhare/etcd,shawnps/etcd,li-ang/etcd,kingland/etcd,jmptrader/etcd,hzy001/etcd,achanda/etcd,bdarnell/etcd,improbable-io/etcd,armstrongli/etcd,sinsharat/etcd,pauldallen/etcd,purpleidea/etcd,OyTao/etcd_learning,endocode/etcd,heyitsanthony/etcd,snailwalker/etcd,xueshanf/etcd,es-chow/etcd,glevand/coreos--etcd,combk8s/etcd,xychu/etcd,honeyqa/etcd,asim/etcd,lzbgt/etcd,bdarnell/etcd,nekto0n/etcd,chenbaihu/etcd,chai2010/etcd,coreos/etcd,rnaveiras/etcd,dannysauer/etcd,lumjjb/etcd,jlamillan/etcd,vimalk78/etcd,fasaxc/etcd,beni55/etcd,mitake/etcd,yichengq/etcd,tangkun75/etcd,insionng/etcd,akauppi/etcd,zaphod-concur/etcd,endocode/etcd,plasticbox/etcd,HideoYamauchi/etcd,xueshanf/etcd,youxidev/etcd,mickep76/etcd,mischief/etcd,cognusion/etcd,mwitkow/etcd,justintung/etcd,dannysauer/etcd,rchicoli/etcd,chipironcin/etcd,robszumski/etcd,dalanlan/etcd,whuwxl/etcd,Yhgenomics/etcd,wantonsolutions/dinv-etcd,axingblog/etcd,pauldallen/etcd,westhood/etcd,steveeJ/etcd,mwitkow-io/etcd,justintung/etcd,jravetch/etcd,gouyang/etcd,buaazp/etcd,swingbach/etcd,etcd-io/etcd,openedbox/etcd,msanterre/etcd,sebschrader/etcd,onlyjob/etcd,Timer/etcd,jchauncey/etcd,plasticbox/etcd,yichengq/etcd,mkumatag/etcd,chai2010-playground/etcd,sebschrader/etcd,msanterre/etcd,delkyd/etcd,mqliang/etcd,visheshnp/etcd,linuxcer/etcd,qqsun8819/etcd,li-ang/etcd,shakefu/etcd,yudai/etcd,mischief/etcd,gae123/etcd,HideoYamauchi/etcd,jonboulle/etcd,pengzj/etcd,qiaochao911/etcd,handsomesun/etcd,offscale/etcd,bspline/etcd,fgbreel/etcd,SivagnanamCiena/etcd,hpcloud/etcd,fanminshi/etcd,csuideal/etcd,fasaxc/etcd,imzhulei/etcd,wowsoso/etcd,coreos/etcd,jlamillan/etcd,raoofm/etcd,nekto0n/etcd,njucslqq/etcd,bakins/etcd,cchamplin/etcd,Yhgenomics/etcd,cchamplin/etcd,tempbottle/etcd,steveeJ/etcd,TheHippo/etcd,nkhare/etcd,youxidev/etcd,jmptrader/etcd,mickep76/etcd,Eagle-X/etcd,cockroachdb/etcd,ajityagaty/etcd,hroyrh/etcd,chai2010-playground/etcd,gouyang/etcd,sayden/etcd,tempbottle/etcd,bakins/etcd,dalanlan/etcd,achanda/etcd,crandles/etcd,fanminshi/etcd,dnaeon/etcd,tguangch/etcd,gityf/etcd,xebitstudios/etcd,yyljlyy/etcd,glycerine/etcd,rnaveiras/etcd,joshix/etcd,elimisteve/etcd,gyuho/etcd,gtank/etcd,etcd-io/etcd,olark/etcd,ajityagaty/etcd,lorneli/etcd,freeloop1114/etcd,lzbgt/etcd,glevand/coreos--etcd,StorReduce/etcd,akauppi/etcd,hroyrh/etcd,qiaochao911/etcd,pigfoot/etcd,shakefu/etcd,cognusion/etcd,honeyqa/etcd,offscale/etcd,ylong/etcd,Eagle-X/etcd,nieanan/etcd,ecnahc515/etcd,fasaxc/etcd,a-robinson/etcd,ecnahc515/etcd,xdlinear/etcd,linuxcer/etcd,tamird/etcd,njharman/etcd,openedbox/etcd,oscarrr110/etcd,dnaeon/etcd,polvi/etcd,glycerine/etcd,iamqizhao/etcd,lorneli/etcd,princeqjzh/etcd,glensc/etcd,mwitkow/etcd,wantonsolutions/dinv-etcd,xebitstudios/etcd,chenbaihu/etcd,QuantiumTechnology/etcd,jonboulle/etcd,devfreesg/etcd,ravigadde/etcd,raoofm/etcd,dterei/etcd,imzhulei/etcd,hongbinz/etcd,jravetch/etcd,betawaffle/etcd,sebrandon1/etcd,visheshnp/etcd,gityf/etcd,qqsun8819/etcd,a-robinson/etcd,buaazp/etcd,hongchaodeng/etcd,heyitsanthony/etcd,njharman/etcd,olark/etcd,bspline/etcd,insionng/etcd,hzy001/etcd,jefby/etcd,rchicoli/etcd,shafreeck/etcd,nieanan/etcd,jeremyeder/etcd,fgbreel/etcd,svdata/etcd,YuleiXiao/etcd,mwitkow-io/etcd,hongbinz/etcd,mqliang/etcd,whuwxl/etcd,mgoelzer/etcd-fork2,gyuho/etcd,csuideal/etcd,sofuture/etcd,kkaneda/etcd,freeloop1114/etcd,hongchaodeng/etcd,es-chow/etcd,polvi/etcd,hpcloud/etcd,svdata/etcd,arthurcolle/etcd,njucslqq/etcd,jchauncey/etcd,junxu/etcd,axingblog/etcd,yyljlyy/etcd,vimalk78/etcd,improbable-io/etcd,ravigadde/etcd,yifan-gu/etcd,mkumatag/etcd,wfxiang08/etcd,joshix/etcd,tguangch/etcd,betawaffle/etcd,swingbach/etcd,asim/etcd,gosharplite/etcd,gtank/etcd,mike-lerch/etcd,glensc/etcd,purpleidea/etcd,beni55/etcd,barakmich/etcd,cockroachdb/etcd,yifan-gu/etcd,oscarrr110/etcd,CrazyJvm/etcd,ajityagaty/etcd,tamird/etcd,barakmich/etcd,sofuture/etcd,xiang90/etcd,mgoelzer/etcd-fork2,siddontang/etcd,wowsoso/etcd,bluebreezecf/etcd,luxas/etcd,yudai/etcd,jefby/etcd,shafreeck/etcd,StorReduce/etcd,QuantiumTechnology/etcd,wantonsolutions/dinv-etcd,handsomesun/etcd,elimisteve/etcd,armstrongli/etcd,zaphod-concur/etcd,kkaneda/etcd,ktateish/etcd,YuleiXiao/etcd,mqliang/etcd,princeqjzh/etcd,tangkun75/etcd,gosharplite/etcd,SivagnanamCiena/etcd,iamqizhao/etcd,giantswarm/etcd,spacejam/etcd,OyTao/etcd_learning,Winslett/etcd,Winslett/etcd,rnaveiras/etcd,chipironcin/etcd,onlyjob/etcd,insequent/etcd