Fix WSGI application

* Partial revert of 0a82af18ab
  to restore main() method
* Add global `application` variable which will be set by main method to
  problem to preserve the fix from 0a82af18ab.
* Add check for application name starting with '_mod_wsgi' to ensure
  application runs in Devstack as well (Devstack does not use the entry point)
* Modify Devstack plugin to run WSGI entry point rather than app/wsgi.py from
  module directory.

Change-Id: I07001dccb663ed4e6e3347089ab96e6f8ec196d4
Story: 2001197
Task: 5702

devstack/plugin.sh

@@ -258,7 +258,7 @@ function configure_monasca_log_api_wsgi {
     fi
 
     # copy proxy vhost and wsgi helper files
-    sudo cp $MONASCA_LOG_API_DIR/monasca_log_api/app/wsgi.py $MONASCA_LOG_API_WSGI_DIR/monasca_log_api
+    sudo cp $MONASCA_LOG_API_BIN_DIR/monasca-log-api-wsgi  $MONASCA_LOG_API_WSGI_DIR/monasca_log_api
     sudo cp $PLUGIN_FILES/apache-log-api.template $monasca_log_api_apache_conf
     sudo sed -e "
         s|%PUBLICPORT%|$monasca_log_api_api_port|g;

monasca_log_api/app/wsgi.py

@@ -18,6 +18,15 @@ Use this file for deploying the API under mod_wsgi.
 
 from paste import deploy
 
-base_dir = '/etc/monasca/'
-conf = '%slog-api-paste.ini' % base_dir
-application = deploy.loadapp('config:%s' % conf)
+application = None
+
+
+def main():
+    base_dir = '/etc/monasca/'
+    conf = '%slog-api-paste.ini' % base_dir
+    app = deploy.loadapp('config:%s' % conf)
+    return app
+
+
+if __name__ == '__main__' or __name__.startswith('_mod_wsgi'):
+    application = main()