[zorg] Update status reporting of reverse-iteration builder

[pzheng]

Summary

The mail notification to "interested users" has been disabled for the
reverse-iteration builder. This patch turns the mail notification on so that
interested users are notified of new failures on the reverse-iteration
builder. Notice that only transitions from pass to fail on the builder will
trigger mail notification. Subsequent failures will not be reported repeatedly.

buildbot/osuosl/master/config/status.py

return [
             subject="Build %(builder)s Failure",
             mode = "failing",
             builders = ["polly-arm-linux",
                         "aosp-O3-polly-before-vectorizer-unprofitable"],
             addLogs=False,
             num_lines = 15),
         InformativeMailNotifier(
             fromaddr = "[e-mail]",
-            sendToInterestedUsers= False,
+            sendToInterestedUsers= True,
             extraRecipients = ["[e-mail]"],
             subject="Build %(builder)s Failure",
-            mode = "failing",
+            mode = "problem",
             builders = ["reverse-iteration"],
             addLogs=False,
             num_lines = 15),
         InformativeMailNotifier(
             fromaddr = "[e-mail]",
             sendToInterestedUsers= False,
             extraRecipients = ["[e-mail]"],
             subject="Build %(builder)s Failure",