Update git submodules

Update git submodules

* Update docs/submodules/fuel from branch 'stable/fraser'
  - [maas] Download only used subarches images

    - reduce download size/time for MaaS images by downloading only the
      subarch images we use;
    - fix stop condition in MaaS artifact download script;
    - stop importing images before updating the boot resources to prevent
      race conditions;

    Change-Id: I3b15fae3463bc6c54be2cc06e0cb31edcbd307cb
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
    (cherry picked from commit 7f797f1b5a9340d24d700879abca6b39413e7375)