Update git submodules

* Update docs/submodules/daisy from branch 'master'
  - Add doc for building kolla image

    Change-Id: I7d25c13221e60d40801dc694efe8c32c31ebfabf
    Signed-off-by: Zhijiang Hu <hu.zhijiang@zte.com.cn>

diff --git a/docs/submodules/daisy b/docs/submodules/daisy
index 81c6480..21086d1 160000 (submodule)
--- a/docs/submodules/daisy
+++ b/docs/submodules/daisy
@@ -1 +1 @@
-Subproject commit 81c6480386c45b9909b1de50970717a5f5f3533e
+Subproject commit 21086d1bce255c464f57bf6bc183894d7d9bbfba