Code review comment for lp://staging/~wallyworld/juju-core/add-machine-parent-getter

https://codereview.appspot.com/10203043/diff/1/state/machine.go
File state/machine.go (right):

https://codereview.appspot.com/10203043/diff/1/state/machine.go#newcode243
state/machine.go:243: return m.st.Machine(parentId)
Unfortunately this is making an assumption that doesn't always hold.

If I am the provisioner, and I have a state.Machine instance, I won't
necessarily have access to state.

Can we have something that returns ParentId() ?

While this method is OK now, I'm wondering how the API changes are going
to impact it.

https://codereview.appspot.com/10203043/