[RFE] Cleanup configuration file structure

[Thomas Bechtold]

Neutron's current configuration structure is difficult to understand:

- it is not clear which services need which configuration file(s) during startup.
- config files end with .ini instead of .conf (which would be automatically recognized by oslo.config)

oslo.config has already support for so called 'default-config-files' and got recently (v3.20.0) support for 'default-config-dirs'[1]. With that it would be possible to start the different services without any -config-file/--config-dir switches if the configuration filenames would be adjusted to the default.
So for eg. neutron-metadata-agent, the configuration file that is automatically read is /etc/neutron/neutron-metadata-agent.conf . So metadata_agent.ini needs to be renamed to neutron-metadata-agent.conf . The same is true for other services.

[1] http://docs.openstack.org/releasenotes/oslo.config/unreleased.html#id3

[Victor Morales (electrocucaracha)]

I'm in favor to have a cleanup here. Specially because having a configuration structure helps during the implementation of WSGI files[1].

[1] https://review.openstack.org/#/c/409351/

[OpenStack Infra (hudson-openstack)]

Change abandoned by Kevin Benton (<email address hidden>) on branch: master
Review: https://review.openstack.org/416595
Reason: This review is > 4 weeks without comment and currently blocked by a core reviewer with a -2. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and contacting the reviewer with the -2 on this review to ensure you address their concerns.