Update git submodules

Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - [baremetal] prx: Fix empty Apache module list

    On low state expansion, apache.server.modules is iterated, and
    since reclass transforms '~' into 'null', an exception is thrown.

    Use an empty string instead (different type will still ensure reclass
    overrides variables from apache service instead of merging the lists).

    While at it, add missing version 'latest' for mod-wsgi pkg.

    Change-Id: I7913483b6a1be545b96de2958c39840940d9c557
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
    (cherry picked from commit 40f907255380dbfc4d808d9f3c768db80c4c8158)