Make "./unrealircd upgrade" return exit codes from stage 2 as well.

Exit status is now documented at https://www.unrealircd.org/docs/Upgrading
and can be used to see the difference between:
* upgrade+configtest OK,
* upgrade OK but configtest failed
* some other failure
* no newer version available
Handy for scripting...

unrealircd.in

@@ -301,6 +301,7 @@ elif [ "$1" = "hot-patch" -o "$1" = "cold-patch" ] ; then
 	fi
 elif [ "$1" = "upgrade" ] ; then
 	@BINDIR@/unrealircd-upgrade-script $*
+	exit
 elif [ "$1" = "genlinkblock" ] ; then
 	@BINDIR@/unrealircd -L
 else