### Motivation
In #269, we added a way to configure external zookeeper servers. However, it was added to the wrong section of the zookeeper config. The `zookeeper.configData` section is mapped directly into the zookeeper configmap.
### Modifications
Move `zookeeper.configData.ZOOKEEPER_SERVERS` to `zookeeper.externalZookeeperServerList`
### Verifying this change
This is a cosmetic change on an unreleased feature.
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