Update git submodules

Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - lib.sh: Add delay after `kpartx -av`

    On rare occassions, mapper bindings created by kpartx take longer
    to show up, leading to errors when we try to mount them on.
    Bring back the hardcoded delay to bypass such issues.

    Change-Id: Ib386c04fc55cd85235a2156dba08fda378e4cdfd
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
    (cherry picked from commit 6b0d21a70be04666fd60a9d4b05d4ad13e192026)