Poke a hole through the proxy for cluster health

Interesting read-only data on the elasticsearch cluster can be found at
_cluster/health, this opens that url in the apache reverse proxy so that
we can see the health of the cluster.

Change-Id: I8d7a2eeec1f02aaa78af5f348b1ae91af76f522d
Merge "Poke a hole through the proxy for cluster health"