Bug 29914: Make check_cookie_auth compare the userid

Bug 29914: Make check_cookie_auth compare the userid

check_cookie_auth is assuming that the user is authenticated if a cookie exists
and that the login/username exists in the DB.

So basically if you hit the login page, fill the login input with a
valid username, click "login"
=> A cookie will be generated, and the sessions table will contain a
line with this session id.
On the second hit, if the username is in the DB, it will be enough to be
considered authenticated.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>