If both are run under the same process, and api_workers >= 2, the server
process will instantiate two oslo_service.ProcessLauncher instances
This should be avoided [0], and indeed causes issues on subprocess and
signal handling: killed RPC workers not respawning, SIGHUP on master
process leading to unresponsive server, signal not properly sent to all
child processes, ...
To avoid this, use the wsgi ProcessLauncher instance if it exists
[0] https://docs.openstack.org/oslo.service/latest/user/usage.html#launchers
Change-Id: Ic821f8ca84add9c8137ef712031afb43e491591c
Closes-Bug: #1780139