Rename events_collector_sample_rate for clarity

This sample rate is only for votes, the previous name implied that it
would affect all events

r2/example.ini

@@ -810,7 +810,7 @@ create_sr_comment_karma = 0
 # class name to style goldvertisement for special events
 goldvertisement_class =
 # Event-collector sample rate for vote events
-events_collector_sample_rate = 0.0
+events_collector_vote_sample_rate = 0.0
 # Event-collector sample rate for submit (new link) events
 events_collector_submit_sample_rate = 0.0
 # Event-collector sample rate for moderator events

r2/r2/lib/app_globals.py

@@ -344,7 +344,7 @@ class Globals(object):
             'spotlight_interest_nosub_p',
             'gold_revenue_goal',
             'invalid_key_sample_rate',
-            'events_collector_sample_rate',
+            'events_collector_vote_sample_rate',
             'events_collector_mod_sample_rate',
             'events_collector_quarantine_sample_rate',
         ],

r2/r2/lib/eventcollector.py

@@ -68,7 +68,7 @@ class EventQueue(object):
     VOTES = {"1": "up", "0": "clear", "-1": "down"}
 
     @squelch_exceptions
-    @sampled("events_collector_sample_rate")
+    @sampled("events_collector_vote_sample_rate")
     def vote_event(self, vote, old_vote=None, event_base=None, request=None,
                    context=None):
         """Create a 'vote' event for event-collector