Fix deployment image change trigger bug

Don't trigger an image tag change when the image repo being checked
doesn't contain the tag defined in the trigger.
It was incorrectly deploying when the repo didn't contain the tag. This fixes that. And it's checking to see if the image id currently deployed is different from the image id associated with the tag that just changed, which means it should deploy. 

Sent from my iPhone

> On Nov 21, 2014, at 12:01 AM, Clayton Coleman <notifications@github.com> wrote:
> 
> In pkg/deploy/controller/image_change_controller.go:
> 
> > @@ -62,8 +62,9 @@ func (c *ImageChangeController) HandleImageRepo() {
> >  					continue
> >  				}
> >  
> > -				_, tag := parseImage(container.Image)
> > -				if tag != imageRepo.Tags[params.Tag] {
> > +				// The container image's tag name is by convention the same as the image ID it references
> > +				_, containerImageID := parseImage(container.Image)
> > +				if repoImageID, repoHasTag := imageRepo.Tags[params.Tag]; repoHasTag && repoImageID != containerImageID {
> Why is this a bug? User said "I want to trigger a new deployment with the image I get from this IR, and put it into this container by name". Why does the image I have to match the container ID?
> 
> —
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