Reset password and forgot username features are not working for subwiki users

Reproduction steps:

• Create a subwiki with "local and global users" (or local users only)
• Create a user on that subwiki with an email address
• Go to the login page of the wiki and click on "forgot password"
• Insert the username of the user and submit the form

Expected result:

• a mail is sent to perform the reset password operation

Obtained result:

• no mail is sent at all

Note that the process works if the entered user is a main wiki user even accessed from subwiki. The root cause of the bug is that the form is accessed using this kind of URL:
http://localhost:8080/xwiki/authenticate/reset which doesn't provide any information about the subwiki.