Update git submodules

* Update docs/submodules/daisy from branch 'master'
  - Enlarge the RAM of the nodes in virtual deployment

    Now the RAM of controller node in virtual deploymeny is only 4GB.

    [root@host-10-20-11-6 ~]# free -h
                  total        used        free      shared  buff/cache   available
    Mem:           3.7G        3.2G        145M        1.7M        408M        191M
    Swap:          4.0G        4.0G        2.3M

    Since the RAM on the deploy server is at least 64GB (see installation
    guide), we can enlarge every node's RAM to improve the performance.

    Signed-off-by: Alex Yang <yangyang1@zte.com.cn>
    Change-Id: Ie4e1297697e349a6b3edf0fa0c54eeeb94255ca8
    Signed-off-by: Alex Yang <yangyang1@zte.com.cn>

diff --git a/docs/submodules/daisy b/docs/submodules/daisy
index 1fd049a..e51c2fb 160000 (submodule)
--- a/docs/submodules/daisy
+++ b/docs/submodules/daisy
@@ -1 +1 @@
-Subproject commit 1fd049a5a3f22d629c3eada67e39081aded8d161
+Subproject commit e51c2fb37bcc4fb2c37dabd3f75cd4a6dc0ae169