Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "AArch64: base image: pre-install salt-minion"
  - AArch64: base image: pre-install salt-minion

    While at it, rename apt repo in foundation node user-data template
    from "salt" to "saltstack", to align with reclass model naming.

    Change-Id: I5b216492349ae187b568884b1ab4046c52b1c6b2
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 7daf7f1..86adce8 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 7daf7f128714021711970557129a23a86cce2a72
+Subproject commit 86adce8b868f1144381134e8f8d2163ee91bb6a1