ZOOKEEPER-4928: Fix ZOO_VERSION not updated during mvn release:prepare
Reviewers: eolivelli, tisonkun
Author: kezhuw
Closes #2259 from kezhuw/ZOOKEEPER-4928-fix-ZOO_VERSION-not-updated-during-release
(cherry picked from commit aeadf574c0463e7e3db092b588033d8347989d4c)
Signed-off-by: Kezhu Wang <kezhuw@apache.org>