Fix an issue that prevents graceful shutdown of controller workers.
cotyledon.Service.terminate function is by definition the graceful
termination function and doesn't have any 'graceful' optional boolean
argument (https://cotyledon.readthedocs.io/en/latest/api.html).
Because of this error, message_listener.wait() was never called in the
consumers' termination functions, so flows could be interrupted before
completion and could leave resources such as load balancer in a
PENDING_* provisioning state.
By default cotyledon.Service terminates the server after a timeout if
the worker could not shutdown itself gracefully. The default value
for the timeout is 300 seconds (set in devstack plugin) and can be
overriden using the graceful_shutdown_timeout setting in octavia.conf
The default value will be updated to a lower value when work on
persistant taskflow will be merged.
Story: 2006603
Task: 36770
Change-Id: I3f776bd018246897c9a889699a2d0ecbbfbb7098
215c4c2284