"Start node" UI button does not allocate node before starting in 1.7

This needed to be done to de-conflate the allocation and power operations, so that nodes may be powered off without deallocating. — you would want a "start node" that doesn't try to allocate in that case.

Suggestions:
 - make the old "start node" button more intelligent, and auto-allocate as necessary
 - change the label on the button depending on whether the node is allocated or not

any more?

> - make the old "start node" button more intelligent, and auto-allocate as necessary

I think that's what we should do. It's pretty clear to me that if you start a 'Ready' node it should be transparently allocated to you and put through deployment.

There is an issue with this change that is somewhat subtle: if you put a button which says "Start" which as a side-effect allocates, then we're really making the "Allocate" action mysterious. The button would need to communicate "Allocate and Start (with default options)" to ensure the action is understandable without reading the state machine, but how do you put that on a button? Maybe:

  [[ Allocate and Start ]]
      (with default options)

Related:

  * bug 1379187, where there is a complaint about OS and Release being on node edit versus being part of the "start" action workflow
  * bug 1378936, which is a quasi-security issue with users being able to change OS & Release of any node (as opposed to only of Acquired nodes)

The only reason this is on 1.7.0 is that I believe this is a behaviour change if compared to 1.6. However, I won't hold the release up for this.