[FIX] website_forum: display correct user image in forum sidebar

Before this commit, on accessing the validation queue in the website forum,
the user image shown in the sidebar is different from the logged in user image.

The cause of issue was the variable passed from the controller and the
variable used for iterating the for loop who are the same, aka user. Thus
the value for 'user' is getting changed. resolved by storing the user value
to a temporary variable and restoring it after the loop.

After this commit, in the validation queue it will show the same logged in
user image in sidebar.

closes odoo/odoo#110904

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>