Update fail2ban.upstart

It was actually a little problematic :)
Update fail2ban.upstart

No longer directly exec the server, do not remove the PID file because it is unnecessary to do so. No longer respawns because Upstart can not track the process with the starter command.
Change Upstart job to track PID of the server

This only works correctly if the client does not fork itself when starting the server (which forks twice further).
Update Upstart job: uses stop command in pre-stop, removes PID file in post-stop
A few final touches on the Upstart job

(a) use static-network-up, since it is more generic than the started networking event
(b) do not hook into network deconfiguration to speed up shutdown
(c) expect fork, per the use of the "-f" option
(d) use a variable for the run directory to make changing it simpler
(e) handle the situation of a left over socket file
(f) use the -f option to be able to track the PID
Merge pull request #686 from CameronNemo/patch-2

Update fail2ban.upstart