Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "Run galera state on slave nodes one by one"
  - Run galera state on slave nodes one by one

    Apply galera state in consecutive order to avoid
    a race condition with database initialization.

    Change-Id: I877bad38777d8469c03cee3b7e96acc875a3a72a
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 4b28a7b..2e4aa7c 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 4b28a7bb0097434381e5a0508ee865a2c2fba9c2
+Subproject commit 2e4aa7c2e95a4eaee40a0a10e107a75494d76a5c