This commit provides an environment option to change the behaviour so
that it's possible to declare any changes shoudl be considered a junit
failure.
This is useful when carrying out idempotent testing to ensure that
multiple runs are safe and any changes should be considered a test
failure.
In a CI test of an ansible role the practice would be to run the role
once without this to configure the test system, and tehn to run a second
time including this environment vairable so that the CI engine
processing the junit report recognise any changes to be a test fail.