Regression: Order of values in graph/legend is inconsistent with plugin output order

[smokris]

In prior releases of Munin (1.x at least), the order in which a plugin outputs values was the same as the order when rendering stacked graphs and legend (#296 notwithstanding).

However, using the latest development release (2.999.6), the graph/legend order is apparently random. For example, the munin_update plugin outputs hostnames in alphabetical order, yet the legend looks like this:

Some plugins output graph_order during the config step; this also seems to be ignored.