Allow namespacing of private registry images

[Cryptophobia]

Right now, if the ECR registry is namespaces in the values.yml is like this:

    registryid: "373147738271"
    hostname: "373147738271.dkr.ecr.us-east-1.amazonaws.com/team_hephy"

The deis-builder still creates image repo in ECR without the namespace.

Error:

Successfully built 2641d630d4e2
Pushing to registry
name unknown: The repository with name 'team_hephy/slack' does not exist in the registry with id '318742728771'
remote: 2018/07/17 16:15:49 Error running git receive hook [Build pod exited with code 1, stopping build.]

The deis-builder will not be able to push because it has not idea of namespacing the images right now. This needs to be fixed in the code.