Bugfix: openstack router list broken in Yardstick container - dovetail

Bugfix: openstack router list broken in Yardstick container - dovetail

Dependancy of python-openstackclient is not constrained.
This patch specify openstacksdk and openstackclient's version according to [1].

This patch apply for bugfix and need to backported to fraser stable branch.
Continual work need to be done in Gambia according to YARDSTICK-1398.

[1]
https://github.com/openstack/requirements/blob/stable/pike/upper-constraints.txt

JIRA: DOVETAIL-728

Change-Id: I57c718e192699ac322150458d18508b06c93d22b
Signed-off-by: rexlee8776 <limingjiang@huawei.com>