Alter is_locked() helper comment
Alter is_locked() helper comment

The is_locked() helper method comment
was created when we used threading2 but
since we don't use it anymore we need to
adjust that comment to reflect the current
usage.

Change-Id: I06051fb2d65b8c871e916d7e64e6056ecff3afda

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