fix(controller): check image for hostname

Older images may still have a hostname in the database. Checking if
it has a hostname in the image name ensures backwards compatibility.
fix(controller): s/util/utils/
fix(controller): append tag to run tasks

Running a one-off admin command currently pulls all images in the
repository (which is horribly slow) and then runs against (:latest) as a
default, which is not always the intended release.
fix(controller): split repo by '/'

This covers all cases of acceptable docker image names. Since namespaces
with '.' in the name is an invalid character, if we tokenize the name
and we still find a '.' in the namespace, it means it has a hostname.

Checking for '/' is necessary for images which are not namespaced, such
as 'deis.is.awesome'.