Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "Update system reclass model"
  - Update system reclass model

    In order to get tacker definitions and latest changes.

    Change-Id: Ib5bf5034f140e708fb596dd4b622f0b2bdee8a59
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 140f2f3..6f1993b 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 140f2f31083b58cf7bfd0900c0ad402bb13a7d7e
+Subproject commit 6f1993bdcec38c4320f0c4d6488d68fcf4f8dda5