OMID-238 Upgrade ZooKeeper and Curator to latest versions

[lucakovacs]

In this change I upgraded two components to the latest releases:

• Zookeeper to 3.8.1
• Curator to 5.4.0

[gjacoby126]

@lucakovacs - Phoenix and Omid both run as part of an HBase cluster. Because of this we usually keep our dependencies in sync with the HBase project, which currently depends on Zookeeper 3.5.7 and Curator 4.2.

The ZK 3.5 line has been EOLed, so all of our projects will need to upgrade eventually. But I'd suggest upgrading HBase first, then Phoenix, then Omid.

By the way, ZooKeeper 3.8 is supposed to be backward-compatible with 3.5, so 3.5 clients such as HBase, Phoenix and Omid should be able to use a 3.8 ZK quorum in a production environment even without this change.

[lucakovacs]

@gjacoby126 Thank you for your suggestions! :) 

We are planning these upgrades in the other components as well. There's already an open PR in HBase and in Hadoop for this change (see: apache/hbase#5013 and apache/hadoop#5345).