Rename memory backend filesystem -> fake filesystem
Rename memory backend filesystem -> fake filesystem

To ensure that no-one gets confused and believes this
is a real filesystem class, rename it to be a name
that clearly tells it is not a real filesystem.

Change-Id: I47b4018ff50019662492e1865d9cac5e8d43d3bf

openstack/taskflow,openstack/taskflow,pombredanne/taskflow-1,jimbobhickville/taskflow,pombredanne/taskflow-1,jimbobhickville/taskflow,junneyang/taskflow,junneyang/taskflow