Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Upgrading image version of HA test of neutron L3 agent

    In line with the updated documentation, this patch upgrades the cirros
    image from version 0.3.5 to 0.4.0 of the HA neutron-l3-agent test

    Change-Id: I352e861f3d3099491ff6f367a3129dc8f3115394
    Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index b5b26bf..71f945d 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit b5b26bfa187c4db16ed4089119371fb164da12cb
+Subproject commit 71f945d3e3ca38e4a954a6475234e176e150d2f7