Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Set nova disk cachemodes to file directsync

    Set nova/libvirt disk cache modes to file directsync to bypass the
    host page cache & prevent instance's kernel panic due to absent
    /dev partition. Caching mode directsync effectively turns all guest
    I/O operations into direct I/O operations on the host, which is the
    NFS client (virtuals) or GlusterFS (baremetals).
    Also return back to hwe kernel as a golden mean between GA & Edge ones.

    Change-Id: I51ab7d0ee71c214ff16b756cfee16e918738b6fd
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index e4f0ae7..4e54382 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit e4f0ae735120b62f2db476b749a81fab5bab9242
+Subproject commit 4e54382989138155100a5cae90d70ca162dab703