Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - [virtual] Reset mtu for compute management bridge

    Use default mtu for br-mgmt in order to resolve the live
    migration failure (cannot recv data: connection timed out)

    Change-Id: I9cee453d87f849e29fc877fff237f8e604f2df53
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>
    (cherry picked from commit b45f3e15ac5581c1e8c44d0a7a1424a1d092834e)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 84fd2fa..9451b4c 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 84fd2fa61325bdc7c680f4f37c776313ca228530
+Subproject commit 9451b4c4e9d8386f3d3e7b6e8a391d89315b41ab