tests/docker-dns-srv: revert Dockerfile change
tests/docker-dns-srv: revert Dockerfile change

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

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