* IT: Switch to OpenJDK8 base image.
Also split the Docker image into a base image and a child image, and
build the base image ahead of time for efficiency's sake. Also upgrade
ZK to 3.4.10.
* Additional comments about ZK upgrades.
* Use OpenJDK8 instead of Oracle for IT docker
* install wget
* Use different docker image
* Revert "Use different docker image"
This reverts commit 5786c03cb49d0ac60a4f06690e483c3284fe4564.
* Revert "install wget"
This reverts commit 8d1d5ec681301f2919b9d994e65e4d436f948a72.
* Revert "Use OpenJDK8 instead of Oracle for IT docker"
This reverts commit 55ea163bb530b1e88c2cccd647f89d75ac90393a.
* Use prebuilt java8 image
* Add comment on docker image