Password confirmation fails on some settings

[schiessle]

Tested on current master

Steps to reproduce

1. setup a fresh Nextcloud
2. Go to the admin settings
3. Change cronjob settings from Ajax to system cron.

Expected behavior:

1. password confirmation dialog ask me for the root password
2. after entering the root password the settings are stored

Actual behavior:

1. Password confirmation dialog shows up twice, even if the password was entered correct
2. after entering the password twice it looks like setting was successful saved but after page reload the cronjob settings are back to "ajax".

cc @nickvergessen