OTLP profiler is not working when using multiple share backends

[Sylvan Le Deunff]

Description
===========
osprofiler driver for opentelemetry (OTLP) fails to export traces when manila service is ran with oslo_service.service.ProcessLauncher (this is the case of API and share).

The root cause seems to be related to the fact that profiler is initialized before forking. Everything works well if profiler is initialized in start method (ie after oslo_service.service.ProcessLauncher create a forks for the child process)

Steps to reproduce
==================

* Configure a jaeger instance (e.g with docker-compose https://paste.openstack.org/show/bAagyVkZZ56YAMIdGzr4/)
* Ensure installed version of osprofiler >= 4.0.0 to have new OTLP driver
* Install python packages required by OTLP driver: opentelemetry-sdk opentelemetry-exporter-otlp
* Add osprofiler middleware to api-paste.ini config file (https://paste.openstack.org/show/bRL1xrarCm05rNWMD3Xl/)
* Configure manila to use OTLP driver for profiler (e.g: https://paste.openstack.org/show/bCjt0HWhh6r5HLkPjD7Q/)
* Start manila components (api, scheduler, share)
* Create a share by calling manila API with tracing info (e.g with curl: https://paste.openstack.org/show/bi742a3EFZzh047EdMyG/)

Expected result
===============
Open jaeger and find a trace that span from manila-api to manila-share.

Actual result
=============
API and shares does not produce traces... But scheduler do!

Environment
===========
1. manila==16.0.0

2. Custom NetApp share driver

3. StandaloneNetworkPlugin

[Vida Haririan (vhariria)]

See additional triage information at https://meetings.opendev.org/meetings/manila/2024/manila.2024-05-30-15.00.log.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/manila/+/920873

[Vida Haririan (vhariria)]

See related comments in manila-dalmatian-m2-bugsquash ethercal https://ethercalc.net/o2qsmjpagsfb