Add zookeeper job/jobboard impl

Create a base implementation of a
jobboard which serves as a place to post
work to be done, a place to get notified of
new work, and a place which can be used to
atomically acquire that work (so that it
can be worked on) as well as transfer that
work from one entity (say when that entity
fails) to another entity (for further
resumption or other policy/code driven
recovery processes).

Implements: blueprint job-reference-impl

Change-Id: I1de1525df0deee612fb14ca36f0415ea7d2f707c
Merge "Add zookeeper job/jobboard impl"