Update zookeeper version to fix Overlapping warning

[Manno15]

Build script was still exporting zookeeper version 3.14.4. Updating that to version 3.7.0 fixes the overlap warning while building with ./bin/build.

WARNING] zookeeper-3.4.14.jar, zookeeper-jute-3.5.9.jar define 101 overlapping classes: 
[WARNING]   - org.apache.zookeeper.proto.GetMaxChildrenRequest
[WARNING]   - org.apache.jute.compiler.JavaGenerator
[WARNING]   - org.apache.jute.XmlInputArchive$XMLParser
[WARNING]   - org.apache.jute.CsvInputArchive$1
[WARNING]   - org.apache.zookeeper.proto.SetACLRequest
[WARNING]   - org.apache.jute.compiler.JLong
[WARNING]   - org.apache.zookeeper.server.quorum.QuorumPacket
[WARNING]   - org.apache.zookeeper.proto.SetSASLRequest
[WARNING]   - org.apache.zookeeper.data.Id
[WARNING]   - org.apache.zookeeper.proto.SyncRequest
[WARNING]   - 91 more...
[WARNING] maven-shade-plugin has detected that some class files are
[WARNING] present in two or more JARs. When this happens, only one
[WARNING] single version of the class is copied to the uber jar.
[WARNING] Usually this is not harmful and you can skip these warnings,
[WARNING] otherwise try to manually exclude artifacts based on
[WARNING] mvn dependency:tree -Ddetail=true and the above output.
[WARNING] See http://maven.apache.org/plugins/maven-shade-plugin/