contrib/raftexample: use bytes.Buffer.String (no 'string()')
contrib/raftexample: use bytes.Buffer.String (no 'string()')

Signed-off-by: Gyu-Ho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

heyitsanthony/etcd,sebrandon1/etcd,glevand/coreos--etcd,rnaveiras/etcd,YuleiXiao/etcd,xiang90/etcd,rnaveiras/etcd,vimalk78/etcd,vimalk78/etcd,a-robinson/etcd,mickep76/etcd,li-ang/etcd,mqliang/etcd,ajityagaty/etcd,etcd-io/etcd,coreos/etcd,visheshnp/etcd,cockroachdb/etcd,mkumatag/etcd,etcd-io/etcd,xiang90/etcd,bluebreezecf/etcd,mqliang/etcd,dannysauer/etcd,whuwxl/etcd,YuleiXiao/etcd,akauppi/etcd,a-robinson/etcd,coreos/etcd,sinsharat/etcd,etcd-io/etcd,mqliang/etcd,mkumatag/etcd,gyuho/etcd,mkumatag/etcd,cockroachdb/etcd,bluebreezecf/etcd,glevand/coreos--etcd,joshix/etcd,fanminshi/etcd,gyuho/etcd,whuwxl/etcd,mickep76/etcd,li-ang/etcd,fanminshi/etcd,heyitsanthony/etcd,sebrandon1/etcd,joshix/etcd,sinsharat/etcd,lorneli/etcd,lorneli/etcd,bdarnell/etcd,rnaveiras/etcd,visheshnp/etcd,akauppi/etcd,dannysauer/etcd,bdarnell/etcd,ajityagaty/etcd,ajityagaty/etcd