Remove one sub test cases from neutron trunk

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>