templates: Fix prompts in NFS first stage after switch to v2019.1

Commit bc9094f4 broke the first stage in many ways, the one being fixed here is the change of the prompts to be expected during autologin and when getting access to the shell.

Tested with:

$ lqa submit -g ./apertis-tests/templates/profiles.yaml \
      --profile apertis-minimal-amd64-uefi \
      -t release:v2021dev1 \
      -t image_date:20200110.0 \
      -t image_name:apertis_v2021dev1-minimal-amd64-uefi_20200110.0 \
      ./apertis-tests/templates/group-minimal-tpl.yaml 
Submitted job group-minimal-tpl.yaml with id 2171368

See https://lava.collabora.co.uk/scheduler/job/2171368