Workaround or missing redirect_info in JaaS.

[petevg]

JaaS deployments were throwing a JujuAPIError because the JaaS
controller does not appear to have implemented redirect_info.

Dropped in a change to catch the error and ignore it in that case.

@tvansteenburgh @johnsca I'm not sure how to test JaaS stuff effectively. To validate that my code works, you can run examples/add_model.py, after editing the file to pass cloud_name="aws" into the call to .add_model.

(Without this change, add_model will fail due to a JujuAPIErrror.)

[johnsca]

I created a more comprehensive refactor in #116 which I'd like to close this PR in favor of if it looks ok to you.

[petevg]

Agree that @johnsca's refactor is more comprehensive. Closing this out ...