Remove unnecessary / from avatar url

So http://localhost:3000//uploads/user/avatar/1/avatar.png
becomes http://localhost:3000/uploads/user/avatar/1/avatar.png

app/models/user.rb

@@ -497,7 +497,7 @@ class User < ActiveRecord::Base
 
   def avatar_url(size = nil)
     if avatar.present?
-      [gitlab_config.url, avatar.url].join("/")
+      [gitlab_config.url, avatar.url].join
     else
       GravatarService.new.execute(email, size)
     end

spec/helpers/application_helper_spec.rb

@@ -73,7 +73,7 @@ describe ApplicationHelper do
       user = create(:user)
       user.avatar = File.open(avatar_file_path)
       user.save!
-      avatar_icon(user.email).to_s.should match("/gitlab//uploads/user/avatar/#{ user.id }/gitlab_logo.png")
+      avatar_icon(user.email).to_s.should match("/gitlab/uploads/user/avatar/#{ user.id }/gitlab_logo.png")
     end
 
     it "should call gravatar_icon when no avatar is present" do