prevent e2e tests to reuse etcd network config of previous tests

dist/functional-test.sh

@@ -45,6 +45,7 @@ setup() {
 
 teardown() {
     docker rm -f flannel-e2e-test-flannel1 flannel-e2e-test-flannel2 flannel-e2e-test-flannel1-iperf flannel-host1 flannel-host2 > /dev/null 2>&1
+    docker run --rm $ETCDCTL_IMG etcdctl --endpoints=$etcd_endpt rm /coreos.com/network/config > /dev/null 2>&1
 }
 
 write_config_etcd() {