fix: change zk announcement log_path to use log_dir + zookeeper.log

1. Removed node link to zookeeper log volume_dir as it is not needed
2. Removed extraneous comments
3. Reconstructed log_path for zookeeper log announcements to use
log_dir + zookeeper.log instead

Squashed commit of the following:

commit 77eaec8148f7bd325f560f85b3afd801bdb09057
Author: Rachel McCuistion <rachel@infochimps.com>
Date:   Thu Mar 13 22:31:21 2014 -0500

    fixing zk log_path to instead use log_dir + zookeeper.log

Change-Id: I077729d38e729bfa5698735dd237acdbe3a69e81