Greeter: Text direction is not updated in password entries

Originally created by @Anonymous on #15169 (Redmine)

I just played around a little bit with some keyboard bugs in the greeter when this problem appeared:

- I select an Afghani keyboard (written RTL)

- I try to set an admin password but then I realize that I can’t type in Afghani

- I go back to the keyboard and language options and select German everywhere
- I reopen the additional options screen and want to type an admin password but my keyboard layout is still RTL and I can’t see if I’m typing in German or in Afghani now

I went back again to the main window and rechose the German layout, and then after two times the additional options screen adjusted and let me type LTR.

Related issues

• Related to #12598
• Related to #14544 (closed)