reddit_base: Stricter User Agent ratelimiting.

This stops ratelimit checking after the first hit so that more specific
matches won't get extra ratelimiting from a more generic match.

r2/r2/controllers/reddit_base.py

@@ -551,6 +551,7 @@ def ratelimit_agents():
     for s in g.agents:
         if s and user_agent and s in user_agent:
             ratelimit_agent(s)
+            return
 
 def ratelimit_throttled():
     ip = request.ip.strip()