Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Add new nova scenarios for rally sanity/full

    Several new NovaServers and NovaServerGroups scenarios available along
    with the recent Rally update.

    Change-Id: Iee27174923da5a1a25991d8ab5e18f1d404b09ef
    Signed-off-by: Juha Kosonen <juha.kosonen@nokia.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 2c58114..639dac6 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 2c581142ad3524b23e109c25d9a1dc2a1ae16514
+Subproject commit 639dac66f284f12021b12e95e12c389f0ed1e645