There are a few issues fixed here:

- The Barbican API service doesn't set a log file, so all the Barbican API
  service logs go to loadwsgi.py.log by default.
- The logs in loadwsgi.py.log are not ingested properly by Fluentd.
- uWSGI logs go to barbican-api.log. This would normally be used as the log
  file for the Barbican API service logs.

This patch makes the following changes to address the above issues:

- All uWSGI logs (from the Emperor and Vassals) go to barbican_api_uwsgi_access.log
  Although these logs aren't strictly all access logs, this follows the existing
  pattern for WSGI logs.
- The Barbican API service logs are written to barbican-api.log instead of
  loadwsgi.py.log. This follows the pattern used by other OpenStack services.
- Fluentd is configured to parse the Barbican API service logs as it would with
  other OpenStack Python services.

Change-Id: I6d03fa8c81c52b6f061514a836bbd15bb6639aaf
Closes-Bug: #1891343