Provide options to override service name and initialize the datastore.

When using the cloudera packages on CentOS 6 (http://www.cloudera.com/content/cloudera/en/documentation/cdh4/latest/CDH4-Installation-Guide/cdh4ig_topic_21_3.html) it is necessary to override the service name as the init script that is provided with the ```zookeeper-server``` package is called ```zookeeper-server``` rather than the expected service name of ```zookeeper``` that is hardcoded into this module.

Additionally, I have created an ```intialize_datastore``` parameter which if set to ```true``` will execute ```/usr/bin/zookeeper-server-initialize --myid=$id``` and then allow the service to start.
single variable doesn't have to be quoted