Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "Bring in Tacker salt formula"
  - Bring in Tacker salt formula

    Install tacker from git repository since there is no ubuntu package yet.

    Change-Id: Ibe4b6486050213df1a545c5c79c43a635bbf6c08
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 18e2ece..5bef2b9 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 18e2ece7f9f1aba3a4bdc031020b97f40e65fb3c
+Subproject commit 5bef2b99e26c798eb0a5deb3010662eeb941344b