Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "lib.sh: Cleanup previous /boot/efi contents"
  - lib.sh: Cleanup previous /boot/efi contents

    Some UEFI firmwares insist on scanning removable drives, even when
    boot entries were deleted from UEFI boot list (board flash).

    To work around this, remove contents of </boot/efi/*>, so scanning
    won't identify any valid EFI binaries.
    Another option would be erasing partition tables, but identifying
    the underlying disk(s) is more complicated, especially when using
    LVM/RAID etc.

    Change-Id: I9949b99b139b1642e3bd8f04de3bd5ef74d1ecc5
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 3803f9f..6726ba6 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 3803f9ff798b5c186e605cb8366b5153ab4e19fc
+Subproject commit 6726ba6362b79527c210487ff37419142d9f93b6