ELK 7 requires some minor changes from the existing ELK 6 config.
Depends-On: Icfa3db5788b25f70ee75411dbaf20d8d4a6a734b
Change-Id: I9815d202a77da0477aea43d714a5def8a24724fa
Tests prometheus, grafana, and centralised logging.
The tests could be improved in future by querying logs in elasticsearch,
and metrics in prometheus.
Change-Id: Iabad035d583d291169f23be3d71931cb260e87ae