Fixes tests after updating the apigee_edge module.

[Jaesin]

There was a changes to how the credentials are stored in the apigee_edge module that broke the tests for this module.

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[Jaesin]

I signed it!

[googlebot]

CLAs look good, thanks!

[Jaesin]

@cnovak It doesn't appear that void-- has the necessary permissions to review/merge a PR.

[cnovak]

LGTM