Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - [baremetal] VCP VM base img: Switch URL to AWS S3

    Mirantis prebuilt base image for VCP VMs (used by salt.control on
    x86_64) has been moved to a new location on AWS S3.

    Change-Id: I9f4a858a1033c3c0a05cba0bd40a8ceac6075615
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 74a5bd6..255742b 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 74a5bd6ae60916c664b0ec902418e3fae234b0c1
+Subproject commit 255742b98efd4ff499a6abc6eb491059fc268d43