don't check image access on ecr or gcr

[jag0k]

If your change requires any additions or changes to the documentation or to the end-to-end test suite, please submit them as 1 or more pull requests against that repo and refer to them here.

requires deis/workflow#1234
requires deis/workflow-e2e#5678

[Cryptophobia]

Per the CI reported error just add a whitespace and the python linting should pass:

elif settings.REGISTRY_LOCATION != 'ecr':

[Cryptophobia]

@duanhongyi do you know if your PR here #90 could have affected this image access check for ECR. @jag0k is reporting problems with ECR registry and registry-secret.