With this commit, the Worker now sends BytesUp and BytesDown for each
of the connections it handles to the Controller in the Status request.
The Controller then persists these fields to the database. There is also
a new trigger to prevent bytes_up and bytes_down to change after a
connection has been closed, as the last update to a session_connection
row should be the one that is performed as part of the connection
closure process.
Jeff Mitchell
Johan Brandhorst-Satzkorn
Irena Rindos
Hugo Vieira