Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Use dovetail docker image opnfv/dovetail:cvp.0.7.0"
  - Use dovetail docker image opnfv/dovetail:cvp.0.7.0

    Change-Id: I45c7e637182ecb8d73a51fea895a4eefc6a1a0e6
    Signed-off-by: xudan <xudan16@huawei.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 672dcd6..d568d6c 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 672dcd6af0de50c026abab58f0483092461b1719
+Subproject commit d568d6c8187e33681addedb871636623ff0707ca