Fix failures in commenting tests.

Restricting users from upvoting their own comments broke some tests.
Switch these tests to downvoting instead.

test/unit/comment_test.rb

@@ -58,7 +58,7 @@ class CommentTest < ActiveSupport::TestCase
           end
 
           dmail = Dmail.last
-          assert_equal("You were mentioned in a \"comment\":http://#{Danbooru.config.hostname}/posts/#{@comment.post_id}#comment-#{@comment.id}\n\n---\n\n[i]#{CurrentUser.name} said:[/i]\n\nHey @#{@user2.name} check this out!", dmail.body)
+          assert_equal("You were mentioned in a \"comment\":/posts/#{@comment.post_id}#comment-#{@comment.id}\n\n---\n\n[i]#{CurrentUser.name} said:[/i]\n\nHey @#{@user2.name} check this out!", dmail.body)
         end
       end
     end

test/unit/user_test.rb

@@ -111,7 +111,7 @@ class UserTest < ActiveSupport::TestCase
       assert(@user.can_comment_vote?)
       10.times do
         comment = FactoryGirl.create(:comment)
-        FactoryGirl.create(:comment_vote, :comment_id => comment.id)
+        FactoryGirl.create(:comment_vote, :comment_id => comment.id, :score => -1)
       end
 
       assert(!@user.can_comment_vote?)