Rename os project usage list to os usage list

There really isn't anything project specific about the command,
it should really just be `os usage list`. For at least one
development cycle we should keep the old command.

Change-Id: I4d1df801576c259b527e87369f3121b94393cfa8

Author: Steve Martinelli

setup.cfg

@@ -131,6 +131,7 @@ openstack.compute.v2 =
     server_unrescue = openstackclient.compute.v2.server:UnrescueServer
     server_unset = openstackclient.compute.v2.server:UnsetServer
 
+    usage_list = openstackclient.compute.v2.usage:ListUsage
     usage_show = openstackclient.compute.v2.usage:ShowUsage
 
 openstack.identity.v2 =