Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Remove tempest_custom from testcases configs

    Change-Id: I1237eaada5257a8c01753837a5820d840b51bff1
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 5a24cb4..a8f1d8e 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 5a24cb4a7db33e693a063f5c2a66406283aa5cfb
+Subproject commit a8f1d8ea374c9538b1d7a223116d8d7d9b783c89