Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "Bugfix: Add case_name as constructor arg for snaps and rally"
  - Bugfix: Add case_name as constructor arg for snaps and rally

    When running healthcheck tier and rally, it complains " __init__() got
    an unexpected keyword argument 'case_name'"

    Change-Id: I078094921f08b457b88beabee60eabf40b657411
    Signed-off-by: Linda Wang <wangwulin@huawei.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 0cbe545..881edc3 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 0cbe545a4ebda5b37b682b46d849198648a7efe1
+Subproject commit 881edc3942e42ccd9088ed9718600c90b0a04e20