contrib: suppress gosimple errors of raftexample
contrib: suppress gosimple errors of raftexample

Travis claimed errors of gosimple like below
(https://travis-ci.org/coreos/etcd/jobs/208098545):
gosimple checking failed:
contrib/raftexample/raftexample_test.go:78:6: should write erri := <-clus.errorC[i] instead of erri, _ := <-clus.errorC[i]
contrib/raftexample/raftexample_test.go:114:10: should write err := <-eC instead of err, _ := <-eC

This commit fixes the errors.

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