Plugins are re-ordered causing signature mis-matches

[zsims]

In some cases, the plugins are re-ordered.

The "canonical" plugins reported by this tool:

[{"github.com/buildkite-plugins/docker-buildkite-plugin#v2.0.0":{"volumes":["./:/usr/local/src/example"],"environment":["STAGE","SYNC_PATH"]}}]

But on the step BUILDKITE_PLUGINS is

[{"github.com/buildkite-plugins/docker-buildkite-plugin#v2.0.0":{"environment":["STAGE","SYNC_PATH"],"volumes":["./:/usr/local/src/example"]}}]