The cluster timeout configuration default value None is documented to mean
tasks never timeout out. Also the documentation states that the timeout
can be overridden for individual tasks.
With the old implementation the timeout parameter given to async_task was
not honored if the cluster timeout was set to None.
Fixes: #335
The old implementation used count_forever test task that never finishes.
If the timeout implementation does not work in the test, the test never
end and you was required to kill the test runner.
Janne Rönkkö