Update git submodules

Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - [virtual] Switch compute nodes to uca repo

    Test of snaps_health_check gets console output of instance, which is
    empty (https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1667033),
    therefore take affected packages of computes from UCA repo.

    Change-Id: I4e13a40dd47caf305efd9f393b3c3cf5a17ef312
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>
    (cherry picked from commit c76d5e92d9e6cdfc614be4a1ed7b9e630c711008)