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 Placement API. Therefore, this patch adds a new
placement_api_uwsgi_config provider as well as a new
placement::wsgi::uwsgi class.
Change-Id: I6e340f551d11e3c003f7873a4ccffba262411e52