jobd.pl: use SIGINT instead of SIGTERM for initial signal

jobd.pl: use SIGINT instead of SIGTERM for initial signal

When jobd.pl needs to kill a job, it first sends an initial signal to
the process group and then if it's not dead within 15 seconds sends a
SIGKILL to it.

Originally we used SIGTERM as the initial signal, but it's better to use
SIGINT so that we can take advantage of "tee -i" in our update.sh script
to avoid losing output.

Anything we're trying to kill should respond just the same to SIGINT or
SIGTERM and exit gracefully so it shouldn't matter except for the
advantage when using tee.

Therefore switch the initial signal from SIGTERM to SIGINT (the final
signal, if needed, will always remain SIGKILL).

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>