Handle the fact that ptrace is a kernel, not distro feature.

We legitimately will upgrade the kernel on 12.04 to 3.13, which then
enables ptrace. Similarly, we will eventually use Ubuntu 16.04.

This change means this code should always work.
Allow override of ES node in monitoring_health

PVB uses monitoring_02 at the moment, but this can change.
Fix up corner cases for overview.js

The event graph for overview.js is in a bit of a state of flux,
so provide args that can help fix these graphs in the transitionary
period:

* migration to bucky
* standardised naming for FQDN
* standard ordering for FQDN in graphite metric names
*