Update git submodules

* Update docs/submodules/daisy from branch 'master'
  - Merge "Fix delete_virtual_network function call"
  - Fix delete_virtual_network function call

    create_daisy_server_network method in VirtualEnvironment class
    calls self.delete_virtual_network, but it doesn't exist,
    actually it should be delete_virtual_network function in module
    libvirt_utils.py.

    Change-Id: I381e916097744827a22d311b275611df38d8e1be
    Signed-off-by: zhongjun <zhong.jun@zte.com.cn>

diff --git a/docs/submodules/daisy b/docs/submodules/daisy
index 1540553..a6f090d 160000 (submodule)
--- a/docs/submodules/daisy
+++ b/docs/submodules/daisy
@@ -1 +1 @@
-Subproject commit 15405530cd0b27f7e2f27d5c889b561569057057
+Subproject commit a6f090d79c2d9152c05ebe606eedfb80d4ea492b