Procfile: use -listen-client-urls instead of -bind-addr

-bind-addr is etcd 0.4 flag, and we should deprecate it.

Moreover, this makes Procfile fit the workflow we mention in the doc,
which helps ourselves find the problem first.

Procfile

@@ -2,4 +2,4 @@
 etcd1: bin/etcd -name infra1 -listen-client-urls http://localhost:4001 -advertise-client-urls http://localhost:4001 -listen-peer-urls http://localhost:7001 -initial-advertise-peer-urls http://localhost:7001 -initial-cluster-token etcd-cluster-1 -initial-cluster 'infra1=http://localhost:7001,infra2=http://localhost:7002,infra3=http://localhost:7003' -initial-cluster-state new
 etcd2: bin/etcd -name infra2 -listen-client-urls http://localhost:4002 -advertise-client-urls http://localhost:4002 -listen-peer-urls http://localhost:7002 -initial-advertise-peer-urls http://localhost:7002 -initial-cluster-token etcd-cluster-1 -initial-cluster 'infra1=http://localhost:7001,infra2=http://localhost:7002,infra3=http://localhost:7003' -initial-cluster-state new
 etcd3: bin/etcd -name infra3 -listen-client-urls http://localhost:4003 -advertise-client-urls http://localhost:4003 -listen-peer-urls http://localhost:7003 -initial-advertise-peer-urls http://localhost:7003 -initial-cluster-token etcd-cluster-1 -initial-cluster 'infra1=http://localhost:7001,infra2=http://localhost:7002,infra3=http://localhost:7003' -initial-cluster-state new
-proxy: bin/etcd -name proxy1 -proxy=on -bind-addr 127.0.0.1:8080 -initial-cluster 'infra1=http://localhost:7001,infra2=http://localhost:7002,infra3=http://localhost:7003'
+proxy: bin/etcd -name proxy1 -proxy=on -listen-client-urls http://localhost:8080 -initial-cluster 'infra1=http://localhost:7001,infra2=http://localhost:7002,infra3=http://localhost:7003'