Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Bottlenecks SSH connectivity broken

    For ping, it set the ssh login username to be ubuntu.
    So need to use ubuntu image rather than cirros.

    JIRA: DOVETAIL-727

    Change-Id: Iaac8c8280a464efe3a431d4eb260c4a0a626e12d
    Signed-off-by: xudan <xudan16@huawei.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index 354a189..e8afeeb 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit 354a18957eb304ed611912cd6fced2a4ff192e0e
+Subproject commit e8afeeb4d039505f998020bad26106640d1f3e4c