rootfs prompt "/ #" produces a warning in lava

[vigneshraman]

kernel-ci rootfs uses "/ #" as shell prompt. This produces a warning in lava.

The string '/ #' does not look like a typical prompt and could match status messages instead. Please check the job log files and use a prompt string which matches the actual prompt string more closely.

https://lava.collabora.dev/scheduler/job/19101745#L1878

For reference, mesa-ci uses lava-shell: as shell prompt. Could we use a different shell prompt to avoid this warning ?