Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - [baremetal] maas state: Retry sync_all on failure

    Change-Id: Ib4aa3f2cb4fc7129d502b4332cd7fedd83a0e1fe
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 5fd088a..51f374b 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 5fd088a583e235d84e638c30f747d1a3a78cd05d
+Subproject commit 51f374b055999fbc121b624424c21ee45d061538