Replace os-client-config to openstacksdk
Replace os-client-config to openstacksdk

Since now os-client-config has been superceded by openstacksdk[1].
So need to replace the os-client-config in zaqarclient to
slove the issue that 'No module named os_client_config'.

[1]:https://docs.openstack.org/os-client-config/latest/

Change-Id: I19bee5f276dcdd9a885fd99b6b656647e28ba139

openstack/python-zaqarclient