Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Merge "Use official Docker images to build local DB"
  - Use official Docker images to build local DB

    JIRA: DOVETAIL-422

    1. Use official Docker images, mongo:3.2.1 and opnfv/testapi:cvp.0.1.0,
       to build local database and testapi service.
    2. Use the stable Docker tag in offline config file.

    Change-Id: I446a4248effc95f6f5aa6a6d90c0d31ef2f60b39
    Signed-off-by: xudan <xudan16@huawei.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index fc706f5..c3e1d8c 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit fc706f5c364f9ad2f9199cdce1fb85cd3c2bfc1f
+Subproject commit c3e1d8cb6bb228058a152fdcdbd8dec0d2457748