jobd/update.sh: restore mirror ref update notifications
When jobd.pl is run with the --quiet/-q option it does
not set the show_progress variable.
update.sh uses the "bang" function to compute before
and after refs in order to send notifications. It
redirects the output of the "bang" command into a before
and then an after file. Unfortunately, unless show_progress
is set, the "bang" function eats all the output so both the
before and after files end up being empty thus preventing
any notifications!
Now the two "bang" commands that generate the before and
after refs files temporarily set show_progress=1 to avoid
this problem.