* move integration tests from ZooKeeper 3.4.x to 3.5.x
* run a subset of our integration tests with ZK 3.4 for backwards compatibility testing.
* remove need to build separate docker-base image
- use multi-stage build for the base image
- use openjdk base image instead of building our own JDK base
- workaround Debian not including MySQL by using MariaDB
- download mysql connector directly instead of using distro version
* fix incorrect openssl command failing on Debian
* keep mysql connector version in sync with pom version
* integration test refactor
* integration test refactor
* refactor integration test
* refactor integration test
* refactor integration test
* refactor integration test
* refactor integration test
* refactor integration test
* refactor integration test
* refactor integration test
* address comments
Xavier Léauté
Maytas Monsereenusorn