Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Bring in ovn based scenario

    OVN based scenario doesn't require conventional gateway
    node since connectivity to external networks and routing
    occurs on compute nodes.

    Change-Id: I81e0d497170d5ffb067adf13b0e46290525f26a6
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 52bd5a8..5c56cba 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 52bd5a8f6c5b27ec3070625a51aea8ff85f5a8db
+Subproject commit 5c56cbad4b65d69ec0b23042ee194e30d1234200