dubbo配置多个注册中心

用法：

<dubbo:registry address="zookeeper://10.0.1.131:2181?backup=10.0.1.132:2181,10.0.1.133:2181" />

 或者

<dubbo:registry protocol="zookeeper" address="10.0.1.131:2181,10.0.1.131:2181,10.0.1.131:2181"/>