Update git submodules

* Update docs/submodules/armband from branch 'master'
  - u/fuel: Bump & rebase for debian_ip lowercase fix

    While at it, revert commit adding "opnfv" user to "libvirt" group,
    as it would break with the current event flow (opnfv user being
    created prior to libvirt group).

    Change-Id: I6f5d578153c33dcddac76bc7bc6b428fe6796b1a
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/armband b/docs/submodules/armband
index a7bc883..4b7e790 160000 (submodule)
--- a/docs/submodules/armband
+++ b/docs/submodules/armband
@@ -1 +1 @@
-Subproject commit a7bc88387c4ffa25b12df949a1dce4c090414334
+Subproject commit 4b7e790d335787ce0837ca47025dd7a14287e52a