Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - lib.sh: base image: Prevent using incomplete img

    In case the previous deploy attempt already copied the base image
    as the VCP image in order to perform offline operations and failed,
    leaving an incomplete image in place, current code might try to use
    it instead of building it from scratch.

    Use the hash-agnostic link names as checkpoints for successful image
    handling.

    Change-Id: I1e99e515e18ba1dec534c520811c127b2b528afe
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 510a5fe..5878c5c 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 510a5fe446dea8513060813794c99e856eff1845
+Subproject commit 5878c5c0c2ca8c78e9a5124452eefe8290ab63cd