[Bug] `dstack` doesn't offer idle instances from the pool

[peterschmidt85]

Steps to reproduce:

1. Defne .dstack.yml (e.g. dev-environment) with gpu set to a name (e.g. A10).
2. Invoke dstack run . -f .dstack.yml
3. Stop the run
4. Ensure the instance is idle
5. Try dstack run . -f .dstack.yml --reuse (or without --reuse or pass the name of the instance to --instance)

Reproduced with dstack Sky (0.18.3)

Actual behavior:

The idle instance is not offered

Expected behavior:

The idle instance should be offered

Notes:

If I edit .dstack.yml and change gpu to 1, then the idle instance is offered.

[jvstme]

Temporary workaround: specify the GPU name in lowercase, e.g. a10