Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "docs: Add details to the installation instruction"
  - docs: Add details to the installation instruction

    Added some text details to the diagrams from
    https://gerrit.opnfv.org/gerrit/#/c/46801/

    Change-Id: Ib761ca2a63e7c9e267c3c5c7bbe659d42bddea5e
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 22bbef8..494595b 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 22bbef86f71a099940e366f11afce777cb0d113c
+Subproject commit 494595bd9e73b2f004b4b9877d46ea6521c7b688