Error on Lock() when part of path has already been created
Fixed the multi-level lock test case.

Clean up after the test so that it is repeatable.
zk.Create() will only create one node, so the parent must already
exist. That's why I changed path to be just one node deep.
Use a separate "/test-multi-level" parent node instead of the "/test"
node used as a lock.
Merge pull request #14 from triggit/master

Error on Lock() when part of path has already been created.