Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - Merge "Align options of glusterfs nova_instances volume" into stable/euphrates
  - Align options of glusterfs nova_instances volume

    Change-Id: If0558afd37f16678290353fa9c5e6c4163f814a0
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>
    (cherry picked from commit 74a5bd6ae60916c664b0ec902418e3fae234b0c1)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 201900a..2e7e259 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 201900ac05e9e9d7cff4984a1bf9d306eadcf14f
+Subproject commit 2e7e259988bc40ff217de6c2035b689f17794162