[r=rvb,jason-hobbs][bug=1375664][author=gmb] Node.start_deployment(), .end_deployment() and .release() now commit the transaction after changing the node's state.
Previously, they merely called node.save(), which was fine for individual node actions but unhelpful at best for bulk actions, because only some of the state changes got committed to the database. This should ensure that *all* state changes will be recorded properly.