This patch enables the use of the WSGI module with the ML2/OVN
mechanism driver. The ML2/OVN requires two events that are called
during the Neutron eventlet server initialization:
* BEFORE_SPAWN: called once before the API workers have been created
and after the ML2 plugin code has been initalizated.
* AFTER_INIT: called when the API worker is started; at this point
the different worker processes have been spawned.
The WSGI module didn't make these event calls. Now these events are
called during the API server initialization, after the ML2 plugin
has been initalizated but before the server is running and attending
any request.
This approach differs from the Neutron eventlet server event calls
because the BEFORE_SPAWN event is called for all API workers; that
means the method ``OVNMechanismDriver.pre_fork_initialize`` is called
as many times as workers are configured.
Closes-Bug: #1912359
Change-Id: I684c6cea620308a6617b665400ce608650a2adfd
Rodolfo Alonso Hernandez
cfab008eef