Display bounty/penalty information only if they would actually be changing anything

This avoid messages like
    Required age reduced by 0 days because of autopkgtest
that is hardly useful.

Signed-off-by: Mattia Rizzolo <mattia@debian.org>

britney2/policies/policy.py

@@ -338,6 +338,7 @@ class AgePolicy(BasePolicy):
         days_old = self._date_now - self._dates[source_name][1]
         min_days = self._min_days[urgency]
         for bounty in excuse.bounty:
+            if excuse.bounty[bounty]:
                 self.logger.info('Applying bounty for %s granted by %s: %d days',
                                  source_name, bounty, excuse.bounty[bounty])
                 excuse.addhtml('Required age reduced by %d days because of %s' %
@@ -345,6 +346,7 @@ class AgePolicy(BasePolicy):
                 min_days -= excuse.bounty[bounty]
         if urgency not in self._penalty_immune_urgencies:
             for penalty in excuse.penalty:
+                if excuse.penalty[penalty]:
                     self.logger.info('Applying penalty for %s given by %s: %d days',
                                      source_name, penalty, excuse.penalty[penalty])
                     excuse.addhtml('Required age increased by %d days because of %s' %