Limit the undo on failures to only stop or scale down

Refactor undo
Merge remote-tracking branch 'origin/pr/219'

Signed-off-by: Dave Liebreich <dliebreich@pivotallabs.com>

Conflicts:
	app/models/runtime/app.rb
	spec/unit/models/runtime/app_spec.rb
Undo both scale and start when undoing changes on applications.

* modify #219 to always undo both scale and start as they can both be changed
  through one request.

[#70554244]

Signed-off-by: Dave Liebreich <dliebreich@pivotallabs.com>
Merge branch 'master' of https://github.com/cloudfoundry/cloud_controller_ng