wal: minor fixes
wal: minor fixes

- remove unnecessary type cast
- simply modulo operations

coreos/etcd,etcd-io/etcd,visheshnp/etcd,mqliang/etcd,dannysauer/etcd,ajityagaty/etcd,lumjjb/etcd,glevand/coreos--etcd,fanminshi/etcd,whuwxl/etcd,OyTao/etcd_learning,YuleiXiao/etcd,bluebreezecf/etcd,luxas/etcd,qqsun8819/etcd,StorReduce/etcd,nekto0n/etcd,bdarnell/etcd,ajityagaty/etcd,li-ang/etcd,insequent/etcd,hongchaodeng/etcd,purpleidea/etcd,rnaveiras/etcd,chipironcin/etcd,mkumatag/etcd,mickep76/etcd,vimalk78/etcd,glevand/coreos--etcd,gyuho/etcd,OyTao/etcd_learning,wantonsolutions/dinv-etcd,lorneli/etcd,jonboulle/etcd,etcd-io/etcd,xiang90/etcd,linuxcer/etcd,bdarnell/etcd,ajityagaty/etcd,purpleidea/etcd,dannysauer/etcd,zaphod-concur/etcd,mqliang/etcd,gyuho/etcd,sebrandon1/etcd,plasticbox/etcd,rchicoli/etcd,a-robinson/etcd,qqsun8819/etcd,heyitsanthony/etcd,rnaveiras/etcd,linuxcer/etcd,swingbach/etcd,nekto0n/etcd,YuleiXiao/etcd,lorneli/etcd,mkumatag/etcd,heyitsanthony/etcd,westhood/etcd,jlamillan/etcd,StorReduce/etcd,sofuture/etcd,hongchaodeng/etcd,ravigadde/etcd,handsomesun/etcd,chipironcin/etcd,swingbach/etcd,westhood/etcd,luxas/etcd,coreos/etcd,CrazyJvm/etcd,ktateish/etcd,insequent/etcd,tguangch/etcd,ktateish/etcd,a-robinson/etcd,whuwxl/etcd,sinsharat/etcd,tguangch/etcd,mqliang/etcd,yudai/etcd,handsomesun/etcd,joshix/etcd,endocode/etcd,sofuture/etcd,CrazyJvm/etcd,rchicoli/etcd,jonboulle/etcd,wantonsolutions/dinv-etcd,akauppi/etcd,xiang90/etcd,glycerine/etcd,vimalk78/etcd,wantonsolutions/dinv-etcd,etcd-io/etcd,plasticbox/etcd,lumjjb/etcd,akauppi/etcd,mickep76/etcd,armstrongli/etcd,armstrongli/etcd,glycerine/etcd,cockroachdb/etcd,sebrandon1/etcd,fanminshi/etcd,yudai/etcd,mkumatag/etcd,visheshnp/etcd,rnaveiras/etcd,li-ang/etcd,jlamillan/etcd,cockroachdb/etcd,zaphod-concur/etcd,joshix/etcd,ravigadde/etcd,sinsharat/etcd,bluebreezecf/etcd,endocode/etcd