classes/conf: Add eventmasks for event handlers

Now that bitbake supports masking events for event handlers, lets use
this so event handlers are only called for events they care about. This
lets us simplify the code indentation a bit at least as well as mildly
improving the event handling performance.

(From OE-Core rev: bff73743280f9eafebe4591f7368ead91a4eb74d)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/bugzilla.bbclass

@@ -71,6 +71,7 @@ def bugzilla_add_comment(debug_file, server, args, bug_number, text):
         return False
 
 addhandler bugzilla_eventhandler
+bugzilla_eventhandler[eventmask] = "bb.event.MsgNote bb.build.TaskFailed"
 python bugzilla_eventhandler() {
     import glob
     import xmlrpclib, httplib