Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - lib.sh: Fix `modprobe -f` on Ubuntu

    For some reason, `modprobe -f` for a clean nbd module (from vanilla
    Ubuntu) fails with exec format error randomly, while a simple
    `modprobe` works.

    Change-Id: I79785e510cab757e2482baf442054be984c24019
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index ea6ecbb..510a5fe 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit ea6ecbb6fb546e27fcc73e699e08c6cad31d2bd0
+Subproject commit 510a5fe446dea8513060813794c99e856eff1845