* 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 5786c03cb4.
* Revert "install wget"
This reverts commit 8d1d5ec681.
* Revert "Use OpenJDK8 instead of Oracle for IT docker"
This reverts commit 55ea163bb5.
* Use prebuilt java8 image
* Add comment on docker image