Add stronger checking of backend configuration
Add stronger checking of backend configuration

Set a default if the backend configuration is not
provided as well as check for the configuration
being a dictionary instead of any arbitary non-false
type.

Change-Id: Id458ac0eb2d7b86c5602ed2f23a52fb2c6f6f0e7

varunarya10/taskflow,citrix-openstack-build/taskflow,jimbobhickville/taskflow,citrix-openstack-build/taskflow,varunarya10/taskflow,junneyang/taskflow,junneyang/taskflow,jimbobhickville/taskflow,pombredanne/taskflow-1,pombredanne/taskflow-1,openstack/taskflow,openstack/taskflow