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 Gnocchi API. Therefore, this patch adds a new
gnocchi_api_uwsgi_config providers as well as a new
gnocchi::wsgi::uwsgi_api class.
Change-Id: Iea9a674be86902be46fdc124e6d0ecf0c1ec8961