fix(zk locking): If there is an error getting children of a node, stop trying to lock and bubble the error up.
fix(zk locking): Refactor things to avoid creating double watches, possibly leaving an extra watch lingering.
fix(ultralight): Remove unused watch function.
fix(ultralight): Use log.error instead of log.warning
Merge pull request #3 from jirwin/jirwin/fix_null_children_error

Fixes a crasher and another potential bug in the locking algo.