Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Set default volume_device_name = vdb

    refstack_defcore is currently failing on all installers.
    It will highlight the right value per installer.

    A better way is to manage the device name by a new env var set by all
    installers (it may depend on kdrive configurations)

    JIRA: FUNCTEST-947
    Change-Id: If1c12bc6798bc89136715bc78f2ac0b798e669e6
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 159ffa7..ce3e130 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 159ffa7b1ec7c6962c0cf08435373557675f9109
+Subproject commit ce3e13025ef35a9c5eb25a7259656e5bf0d57213