Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Merge "Fix the docker version to be 1.12.3 in Dovetail docker image"
  - Fix the docker version to be 1.12.3 in Dovetail docker image

    JIRA: DOVETAIL-442

    Change-Id: I476c2dabf5b23ed42a0004d8d3a9e17727051eca
    Signed-off-by: xudan <xudan16@huawei.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index d7795dd..d40ffff 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit d7795dd0b6e10c335dba65f1456d43fee50c121f
+Subproject commit d40ffffeb0fc4aea0dc5d1cfac2c7be1f94b8392