Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Remove one sub test cases from neutron trunk

    There is one sub test case that can't work correctly on Mitaka,

    neutron.tests.tempest.api.test_trunk.TrunkTestJSON.test_create_update_trunk_with_description

    It will get a 'Bad request' error.
    Details: {u'message': u"Unrecognized attribute(s) 'description'",
    u'type': u'HTTPBadRequest', u'detail': u''}.

    That's mainly because of that,

    For Mitaka, there's only several extension resources that support
    attribute 'description', which is 'security_group_rules', 'security_groups',
    'ports', 'subnets', 'networks', 'routers', 'floatingips' and 'subnetpools'.
    All other extension resources including trunk port can't create with description.

    See https://github.com/openstack/neutron/blob/mitaka-eol/neutron/extensions/standardattrdescription.py#L22

    For Newton, all subclasses of class 'HasStandardAttributes' support
    the attribute 'description' including class Trunk.

    See https://github.com/openstack/neutron/blob/newton-eol/neutron/extensions/standardattrdescription.py#L49,
    https://github.com/openstack/neutron/blob/newton-eol/neutron/db/standard_attr.py#L158
    and
    https://github.com/openstack/neutron/blob/newton-eol/neutron/services/trunk/models.py#L26

    JIRA: DOVETAIL-723

    Change-Id: Ifdfea7c54a1888d933c8ddd78a6feea1db93368c
    Signed-off-by: xudan <xudan16@huawei.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index 8e049de..839377b 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit 8e049deb6d5829a63c50d77c19be5040e8328f20
+Subproject commit 839377b3b9c18ebf73cd6a7bfeb85d73f548d6b7