add details to newrelic trace, fix 401 errors for xml

app/controllers/application_controller.rb

@@ -58,6 +58,10 @@ protected
         render :text => "authentication failed", :status => 401
       end
 
+      fmt.xml do
+        render :xml => {:sucess => false, :reason => "authentication failed"}.to_xml(:root => "response"), :status => 401
+      end
+
       fmt.json do
         render :json => {:success => false, :reason => "authentication failed"}.to_json, :status => 401
       end

app/models/post.rb

@@ -1034,7 +1034,7 @@ class Post < ActiveRecord::Base
     end
 
     def fast_count_search(tags, options = {})
-      count = Post.with_timeout(options[:statement_timeout] || 500, Danbooru.config.blank_tag_search_fast_count || 1_000_000) do
+      count = Post.with_timeout(options[:statement_timeout] || 500, Danbooru.config.blank_tag_search_fast_count || 1_000_000, :tags => tags) do
         Post.tag_match(tags).count
       end
       if count > 0