This patch is adding the configuration of the number of workers,
threads, and the size of the listen queue in Debian, which uses
uwsgi to run Octavia API. Therefore, this patch adds a new
octavia_api_uwsgi_config provider as well as a new
octavia::wsgi::uwsgi class.
Change-Id: I89e2bb5bb127020adcaabe26e62f68123fab3990