The plan step has a mechanism to use the default tf version from the Terraform
client if the context does not define one, however the apply step does not have
this. This results in remote executions of apply failing with a nil pointer
dereference when it checks tfVersion in StripRefreshingFromPlanOutput. This fix
involves copying what the PlanStepRunner does and falls back to the default
version if the context's version is nil.
6dda3dfde1