fix the test that was supposed to break
fix the test that was supposed to break

The test for this behavior did not work, because the old mock diff
function does not work correctly. Write a PlanResourceChange function to
return a correct plan.

tommynsong/terraform,rnaveiras/terraform,pdecat/terraform,tommynsong/terraform,ewbankkit/terraform,tommynsong/terraform,rnaveiras/terraform,apparentlymart/terraform,ewbankkit/terraform,apparentlymart/terraform,ewbankkit/terraform,hashicorp/terraform,apparentlymart/terraform,hashicorp/terraform,pdecat/terraform,hashicorp/terraform,pdecat/terraform,ewbankkit/terraform,apparentlymart/terraform,pdecat/terraform,apparentlymart/terraform,rnaveiras/terraform