Update git submodules

* Update docs/submodules/armband from branch 'stable/danube'
  - bootstrap, dea_base, nailgun: Pin 4.8.0-9944 krn

    New kernel includes:
    - ABI bump;
    - GICv3-ITS live migration support;

    TODO: build meta package so we don't have to bump it manually.

    JIRA: ARMBAND-171

    Change-Id: I4aaa5ca496e535abed948d2e51a6caf7e03393a8
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
    (cherry picked from commit 06a8e925413c3ed0019c714eb83dab2ae179d641)

diff --git a/docs/submodules/armband b/docs/submodules/armband
index 0dbeeae..4e7d0da 160000 (submodule)
--- a/docs/submodules/armband
+++ b/docs/submodules/armband
@@ -1 +1 @@
-Subproject commit 0dbeeaede259f31dfbcc0fdb473f969c23bd4d19
+Subproject commit 4e7d0da731209a64cf0f2a7640bbe3e53723473d