Distinguish notice saving errors from others for Salmon

plugins/OStatus/lib/salmonaction.php

@@ -109,6 +109,8 @@ class SalmonAction extends Action
             // duplicate? Maybe someone's database is out of sync?
             // Let's just accept it and move on.
             common_log(LOG_INFO, 'Salmon slap carried an event which had already been fulfilled.');
+        } catch (NoticeSaveException $e) {
+            common_debug('Notice::saveActivity did not save our '._ve($this->activity->verb).' activity, trying old-fashioned salmon saving.');
         }
 
         try {