jjb: Print only the summary on IRC on Lava job failure

jjb: Print only the summary on IRC on Lava job failure

When detecting a failure on a Lava job, the IRC bot would print all the
new commits on the tracked branches. This would case large amount of
text being printed on the IRC chat room. This sets the bot to only print
the job name that failed.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>