User manual troubleshooting section should include accessing restricted ZooKeeper values

For a variety of troubleshooting steps on the mailing list we tell people to "look in zookeeper"

This snippet from kturner on what that practically means should be added to the troubleshooting section of the user manual.

Use zkCli.sh and look in /accumulo/<accumulo instance id>

In 1.4 Accumulo started locking its info in zookeeper down, so you may need to execute the following command :

addauth digest accumulo:SECRET

Replace SECRET with the secret from your accumulo-site.xml file.