Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - Drop infinite loops in favor of finite wait_for

    While at it, fix some shellcheck warnings, and s/fgrep/grep -F/g.

    Change-Id: I093b7b4c196731b1ecc0c27a4111955b2e412762
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
    (cherry picked from commit 089585ad5370109d4c2a476b94b0017153d7713d)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index ea64dc2..cfd0fcc 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit ea64dc22ea171d45ae60aff682fcadf9d525889b
+Subproject commit cfd0fcc90fa3a3c67289ca4fba26e725f317e4c2