Comment 1 for bug 1131608

Short list of tasks we definitely need to do, one way or another, before we can fix this:

1) add a Series field to state.Machine
2) fix unit assignment to require a machine of the appropriate series (hm, series field on Unit, to avoid having to look up service? will that help anything?)
3) change the environs.Environ interface to accept series(+constraints), not tools, on StartInstance