Fix Idempotent Test

[apmarshall]

The goal of the idempotent test is to let us know when we are following bad practices for ansible playbooks. Unfortunately, it is impossible for shell commands to be truly idempotent and there are other things that inevitably change (ie, git clones) or could easily change and not be an indicator of bad practice (ie, if an update to a package happened to come out between runs).

To improve the situation, we need to do two things:

1. Label tests that cannot be reliably made idempotent with the tag “not-idempotent” so that they are skipped by this test.
2. Add changed_when and failed_when fields to shell command tasks, which will give them something resembling idempotent status.

This is relatively low priority.