sos: fix missing backport of add_alert

fixes add_alert -> addAlert backport from sos 3.y to 2.y

Change-Id: I3469fc13cfd1ece311476a5c1a5200f294763587
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>
(cherry picked from commit a0e280011c1b8f310d24689f6ee1033deffb81b1)