Update git submodules

* Update docs/submodules/armband from branch 'master'
  - p/fuel: Add opnfv user to libvirt group

    Change-Id: Ia075a790fce0aeb0d21b20b2775e2cc079311b88

diff --git a/docs/submodules/armband b/docs/submodules/armband
index 3f5c1de..a7bc883 160000 (submodule)
--- a/docs/submodules/armband
+++ b/docs/submodules/armband
@@ -1 +1 @@
-Subproject commit 3f5c1defe0ce6fa69042f57db6ca9116f7be048b
+Subproject commit a7bc88387c4ffa25b12df949a1dce4c090414334