Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Use dovetail latest docker image cvp.0.8.0

    Change-Id: I87ad5599f5a44074eb67502b02bd2083a773772d
    Signed-off-by: xudan <xudan16@huawei.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 542a88c..68294f0 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 542a88c67f869abd95bb374fd05ab36f8a32d2e4
+Subproject commit 68294f08d466e5e59195158556e26a098685dc5d