Update git submodules

* Update docs/submodules/armband from branch 'master'
  - Merge "docs: Experimental features note about ceilometer"
  - docs: Experimental features note about ceilometer

    Starting with Danube.1.0, Ceilometer and MongoDB are experimental
    in upstream Fuel@Openstack, so the appropiate feature group needs
    to be enabled during master node installation to use them.

    Change-Id: Ib522c7e81cc73625128296873b4f9eef7cf1e99d
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/armband b/docs/submodules/armband
index e2c5709..a781943 160000 (submodule)
--- a/docs/submodules/armband
+++ b/docs/submodules/armband
@@ -1 +1 @@
-Subproject commit e2c57098e2a23c05a0f0a17d59059cd3425bfa9a
+Subproject commit a78194365f19f627d12ee20d643ab5e89966fd42