Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - Adjust memory allocation size

    * [baremetal] add memory to contollers & salt master
    * tune up sysctl vm.dirty* for compute nodes
    * upgrade packages to get the latest versions
      (https://bugs.launchpad.net/cinder/+bug/1641312)

    Change-Id: I9ad22206f2f3f11e1da3f93c7a0931c592adf1cf
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>
    (cherry picked from commit 87310fb8edfe49b9621fe4410ae52d989072e3c5)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 0448121..b0c72d0 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 0448121a5e0a3c1667e1af61fcfb8a51b17fdcfd
+Subproject commit b0c72d0c9bf3ccdf2549d9f5ddeca49085aae636