Added default values for configuration variables

[alexandrst88]

No description provided.

[alexandrst88]

Seems like tests failed due to

TASK [role_under_test : Download zookeeper version.] ***************************
fatal: [localhost]: FAILED! => {"changed": false, "dest": "/opt/src/zookeeper-3.4.12.tar.gz", "msg": "Request failed", "response": "HTTP Error 404: Not Found", "state": "absent", "status_code": 404, "url": "http://www.us.apache.org/dist/zookeeper/zookeeper-3.4.12/zookeeper-3.4.12.tar.gz"}
 [WARNING]: Could not create retry file```

[seancdugan]

Probably would want to pull from the archive url that will maintain the version. https://archive.apache.org/dist/zookeeper/zookeeper-3.4.12/zookeeper-3.4.12.tar.gz