Deploy: Preventative measure to fail deploys early when the associated...

... ELB and ASG have a different size. Fundamentally, this ensures that both the ASG and the ELB have the same number of hosts and that all of those hosts are healthy. This is the first check performed by an autoscaling backed deploy to ensure a deployable state. Prior to this, CAPI were seeing deploys fail through timing out because the waitForStabilization check would never resolve given an inconsistent state from the start, giving the deploy no chance of passing from the get go. This should allow the deploy to fail fast and not leave the application in a state of which needs to be tidied up by a developer (best case).