FIX: crawler requests not tracked for non UTF-8 user agents

Non UTF-8 user_agent requests were bypassing logging due to PG always
wanting UTF-8 strings.

This adds some conversion to ensure we are always dealing with UTF-8

lib/middleware/request_tracker.rb

@@ -117,7 +117,12 @@ class Middleware::RequestTracker
     }
 
     if h[:is_crawler]
-      h[:user_agent] = env['HTTP_USER_AGENT']
+      user_agent = env['HTTP_USER_AGENT']
+      if user_agent.encoding != Encoding::UTF_8
+        user_agent = user_agent.encode("utf-8")
+        user_agent.scrub!
+      end
+      h[:user_agent] = user_agent
     end
 
     if cache = headers["X-Discourse-Cached"]