Dockerfile: remove "cmd/vendor"
Dockerfile: remove "cmd/vendor"

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

coreos/etcd,glevand/coreos--etcd,heyitsanthony/etcd,bdarnell/etcd,lorneli/etcd,rnaveiras/etcd,whuwxl/etcd,etcd-io/etcd,vimalk78/etcd,lorneli/etcd,rnaveiras/etcd,mqliang/etcd,bdarnell/etcd,fanminshi/etcd,sebrandon1/etcd,ajityagaty/etcd,glevand/coreos--etcd,joshix/etcd,mkumatag/etcd,mqliang/etcd,xiang90/etcd,cockroachdb/etcd,mkumatag/etcd,gyuho/etcd,heyitsanthony/etcd,dannysauer/etcd,ajityagaty/etcd,etcd-io/etcd,ajityagaty/etcd,mqliang/etcd,cockroachdb/etcd,sinsharat/etcd,sinsharat/etcd,li-ang/etcd,whuwxl/etcd,gyuho/etcd,rnaveiras/etcd,dannysauer/etcd,vimalk78/etcd,sebrandon1/etcd,etcd-io/etcd,coreos/etcd,xiang90/etcd,li-ang/etcd,joshix/etcd,mkumatag/etcd,fanminshi/etcd