This adds a job that will query the Elasticsearch HTTP cat API to
determine whether the desired number of nodes have been discovered
via the Zen discovery mechanism to be included in the cluster.
This aims to address issues seen when upgrading Elasticsearch,
where the snapshot repository job may trigger due to endpoints
from older pods being present. This new job will be the dependency
required by the snapshot repository job to ensure the ES cluster
has the desired number of nodes before attempting to register a
snapshot repository or interact with the cluster
Change-Id: I94fbbfdec7ca66d04acca9558e56dca3b2bc7d52
8193542c98