Update git submodules

* Update docs/submodules/armband from branch 'master'
  - states/maas: rm Ubuntu boot entry on EFI systems

    MaaS relies on IPMI to set boot order to PXE first; however
    on systems with buggy firmware or without full IPMI support,
    that fails, leading to booting Ubuntu from hard disk instead.

    Work around this by clearing any previous Ubuntu boot entry
    from board flash via `efibootmgr`.

    Change-Id: I531d4bcb9f8d45740764f0dbab8fda49fbffac7e
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/armband b/docs/submodules/armband
index 4acb9cb..aa6c72b 160000 (submodule)
--- a/docs/submodules/armband
+++ b/docs/submodules/armband
@@ -1 +1 @@
-Subproject commit 4acb9cb824de19c8cb5eb73401529a51ce1de561
+Subproject commit aa6c72b42783a4226c07e0b7af37434f13dc8c64