Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - salt.sh: Pin MaaS formula to last known stable ver

    Recent upstream changes broke MaaS machine status parsing. Pin
    the formula to the previous version until upstream provides a
    fixed package or a repo snapshot baseline.

    Change-Id: I26ebd60f40812ae47da0ca28d19c9fdcac7920da
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index eb46452..c4b87db 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit eb4645206d6d74992fca3b8726ee2eebca97205f
+Subproject commit c4b87dbc189e2a2f4d586d41ef5db2166c42231d