Logging in with a global user to a subwiki which has only local users option should not work

Steps to reproduce:

• create a local user on main wiki (let's say sorinello). This user should not be Admin
• when logged in as Admin from the main wiki, create a subwiki with the following options:
  • Only local users are available in the wiki
  • Open for any user to join
• from another browser, login to the main wiki using the sorinello user. Go to wiki index, and click "join" to join the subwiki. (we do this as a workaround to http://jira.xwiki.org/browse/XWIKI-9726)
• go to the subwiki, and you are able to login to the subwiki, even if you are a global user.

So you can login with a global user to a subwiki which has the "Only local users are available in the wiki " option set.