Update git submodules

* Update docs/submodules/clover from branch 'stable/fraser'
  - Add support for install istio of specified version

    Change-Id: Ibfe0002daff58d30e7fffbb8828d8853a7e963a6
    Signed-off-by: Yujun Zhang <zhang.yujunz@zte.com.cn>
    (cherry picked from commit f119c6b855e4b6709b5cbf44b46d6046841108ea)

diff --git a/docs/submodules/clover b/docs/submodules/clover
index ffd7c93..bb52b9c 160000 (submodule)
--- a/docs/submodules/clover
+++ b/docs/submodules/clover
@@ -1 +1 @@
-Subproject commit ffd7c93b70144f412cd90601646730a2773c2ea3
+Subproject commit bb52b9c4235e622dfb08bf7cf674f4daabc1cff6