Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "[virtual] Update dpdk scenario with pike"
  - [virtual] Update dpdk scenario with pike

    Change-Id: I879f565fe17539a54770fa22a6088c6493524e0c
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index a384976..81ee9b1 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit a384976c68f07017bca993cdbe578061ec539890
+Subproject commit 81ee9b180ab11507492783aa1d62927faa9876df