Change url download for ZK
<!-- Version of Solr should be retrieved from a property file as well
as the SHA1 -->
- <url>http://www-eu.apache.org/dist/zookeeper/zookeeper-${zookeeper.version}/zookeeper-${zookeeper.version}.tar.gz</url>
+ <url>http://archive.apache.org/dist/zookeeper/zookeeper-${zookeeper.version}/zookeeper-${zookeeper.version}.tar.gz</url>
<sha1>eb2145498c5f7a0d23650d3e0102318363206fba</sha1>
