CA DRA: add integration tests for disabled DRA flag

[towca]

Which component are you using?:

/area cluster-autoscaler
/area core-autoscaler
/wg device-management

Is your feature request designed to solve a problem? If so describe the problem this feature should solve.:

All existing unit tests are run with DRA enabled whenever possible, to cover more code paths and ensure that the behavior stays the same when DRA is enabled but there are no DRA objects. These tests should also cover the "DRA is disabled and there are no DRA objects" case, as the flag just enables more codepaths. The "DRA is enabled and there are DRA objects" case has a lot of integration tests, but we're missing coverage for the "DRA is disabled and there are DRA objects" case.

Describe the solution you'd like.:

We should add some integration tests for the "DRA is disabled and there are DRA objects" case to ensure that CA still behaves in a sane way.

Additional context.:

This is a part of Dynamic Resource Allocation (DRA) support in Cluster Autoscaler. An MVP of the support was implemented in #7530 (with the whole implementation tracked in kubernetes/kubernetes#118612). There are a number of post-MVP follow-ups to be addressed before DRA autoscaling is ready for production use - this is one of them.