When going to the installer (without the DB structure), you have to log
twice before starting the installation.
Test plan:
0/ Create a new database and fill the database entry in the koha conf
with its name
1/ Go on the mainpage, you should be redirected to the installer
2/ Try to log in
Without this patch, you will get the login form again.
With this patch, you can start the installation
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>