Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Conform with Docker ARCH names

    It switches Docker tags:
      - x86_64 -> amd64
      - aarch64 -> arm64

    Change-Id: I05575dd728e7502a891a3ee3015f81ac8e3f7a92
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index b31ae2c..a8acc48 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit b31ae2c8b59619251cffcba1f307e0b7b9acd89d
+Subproject commit a8acc48148313229b4e6771374ece9256d75b26c