Add namespace parameter to workflow-get and workflow-get-definition
Add namespace parameter to workflow-get and workflow-get-definition

* '--namespace' paramter was missing in these two commands. Now
  they are added.
* Fixed wrong parameter descriptions
* Style changes

Change-Id: Icce73a247e67268a60de56008e42560225990b68

openstack/python-mistralclient,openstack/python-mistralclient