Code review comment for lp://staging/~sinzui/juju-ci-tools/azure-arm

Thank you. I sorted out a few issues.

1. Logging works. We cannot use our common logging setup because azure's lib will spam our logs.
2. tests.TestCase.test_environ now exists so that tests can easily setup a starting environ
3. dry_run became read_only in the AzureARMClient to be clear that the client is not allowed to make changes.