Kolla is setting the producer tasks to None, and this
disables all producer tasks.
Starting with the next release of Designate a new task
was added to the producer named increment_serial that
is now critical path for incrementing the serial for each zone.
fb9c2da977
Closes-Bug: #1879557
Change-Id: Ief8dca4e27197c9576e215cbd960da75f6fdc20c