This updates dib stats after creating a dashboard to use them.
Firstly, the individual return codes and runtime for each image type
are unnecessary, because they call come from the same invocation of
dib. While it is definitely useful to track the size of each output
image, the overall status for a build is only a single value. This
moves these duplciated values to ".status.<rc|duration>".
Unfortunately, there's really no way to say "what was the time of the
last non-null value" in grafana+graphite [1]. This means you can't do
something useful like show a singlestat of the relative time of the
last build "X hours ago" using the timer value. We can work around
this by putting the timestamp of the last build in a gauge value; this
monotonically increases and is easy to turn into a relative time.
[1] https://github.com/grafana/grafana/issues/10550
Change-Id: Ia9518b6faecb30d45e0509bda4a9b2ab7fdc6261
Ian Wienand