Allow specify the tenant in user.
Allow specify the tenant in user.

- This is to allow the -U tenant:user syntax like previously supported
  when not using the os_ arguments.

sohonetlabs/python-swiftclient,citrix-openstack-build/python-swiftclient,citrix-openstack-build/python-swiftclient,VyacheslavHashov/python-swiftclient,JioCloud/python-swiftclient,chmouel/python-swiftclient,JioCloud/python-swiftclient,krnflake/python-hubicclient,jeseem/python-swiftclient,openstack/python-swiftclient,varunarya10/python-swiftclient,cbrucks/Federated_Python-Swiftclient,ironsmile/python-swiftclient,iostackproject/IO-Bandwidth-Differentiation-Client,sohonetlabs/python-swiftclient,ironsmile/python-swiftclient,citrix-openstack/build-python-swiftclient,citrix-openstack/build-python-swiftclient,iostackproject/IO-Bandwidth-Differentiation-Client,cbrucks/Federated_Python-Swiftclient,pratikmallya/python-swiftclient,cbrucks/Federated_Python-Swiftclient,pratikmallya/python-swiftclient,openstack/python-swiftclient,jeseem/python-swiftclient,chmouel/python-swiftclient,zackmdavis/python-swiftclient,zackmdavis/python-swiftclient,citrix-openstack/build-python-swiftclient,VyacheslavHashov/python-swiftclient,varunarya10/python-swiftclient