[Spot/Serve] Fix controller resources fetching

[Michaelvll]

The previous code fetch the controller record with the wrong name causing the controller fail to use the same resources when starting a service/spot job when the controller already exists.

To reproduce:

1. Have a serve controller on AWS
2. sky serve up --cloud gcp ...
   The service launching command will fail with the following error:

sky.exceptions.ResourcesMismatchError: Requested resources do not match the existing cluster.
  Requested:    {1x GCP(cpus=4+, disk_size=200, ports=['30001-30100'])}
  Existing:     1x AWS(m6i.xlarge, disk_size=200, ports=['30001-30100'])

Tested (run the relevant ones):

• Code formatting: bash format.sh
• Any manual or new tests for this PR (please specify below)
  • The reproducible scripts above
• All smoke tests: pytest tests/test_smoke.py
• Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• Backward compatibility tests: bash tests/backward_comaptibility_tests.sh

[concretevitamin]

When controller exists, why return controller_resources_to_use (which is copied from default resources) rather than that controller’s launched resources?

[Michaelvll]

I suppose the default controller resources can always be scheduled on existing controller, but changed to the existing resources for clarity.