The default TaskFlow engine is now set to 'parallel' instead of
'serial'. The parallel engine schedules tasks onto different threads to
allow for running non-dependent tasks simultaneously. This has the
benefit of accelerating the execution of some Octavia Amphora flows such
as provisioning of active-standby amphora loadbalancers.
Change-Id: I108b7f629d39c40b60ddf4a1878631f32e37b357
0978c776a2