[Bug]: Runs with volumes fail on a3-highgpu-8

[r4victor]

Steps to reproduce

1. Submit a run with volume on a3-highgpu-8
2. Get an error:

Run failed with error code EXECUTOR_ERROR.
Error: prepareVolumes error: failed to create mount point: mkdir /dstack-volumes: read-only file system
Check CLI, server, and run logs for more details.

Actual behaviour

The error was introduced when transitioning to the COS image for a3-highgpu-8 (#2549). The COS root filesystem is not writable, so dstack fails to mount volumes there. The volumes should be mounted at /mnt/disks. See for more details https://cloud.google.com/container-optimized-os/docs/concepts/disks-and-filesystem

Expected behaviour

No response

dstack version

master

Server logs

Additional information

No response