Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - Merge "reclass: apt_mk_version: 2017.12" into stable/euphrates
  - reclass: apt_mk_version: 2017.12

    Although previous commit e3bc5ad changed the first reference of
    apt-mk repos to '2017.12' from 'nightly', it missed the cluster model.

    This fixes redeploys with `-f`, which fail due to conflicts between
    already installed '2017.12' packages and 'nightly' ones.

    Fixes: e3bc5ad

    Change-Id: I854bac86feaaa61da0b68d158e270eec1ee0ccb7
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 0c7d890..c24aa2e 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 0c7d890cdb20fdcf2a5e0e0a629088ee045cf4af
+Subproject commit c24aa2e8919bc13f14236677503983075e35f562