[Bug]: Getting unrelated offers when trying to run multi-node task on unsupported backend

[jvstme]

Steps to reproduce

Prepare a multi-node task configuration with instance volumes.

type: task
commands:
- sleep infinity
nodes: 2
volumes:
- /tmp:/tmp

Try running the task on a backend that does not support multi-node tasks, e.g. RunPod.

> dstack apply -b runpod

Actual behaviour

dstack suggests offers from an unrelated backend, e.g. CUDO.

> dstack apply -b runpod                         

 #  BACKEND  REGION         INSTANCE         RESOURCES                   SPOT  PRICE     
 1  cudo     ca-montreal-1  intel-broadwell  2xCPU, 8GB, 100.0GB (disk)  no    $0.0276   
 2  cudo     ca-montreal-2  intel-broadwell  2xCPU, 8GB, 100.0GB (disk)  no    $0.0286   
 3  cudo     fi-tampere-1   intel-broadwell  2xCPU, 8GB, 100.0GB (disk)  no    $0.0383

Expected behaviour

dstack does not suggest any offers.

dstack version

0.18.35

Server logs

Additional information

No response