unity-greeter wrong language on PAM messages

[Luan Welter]

to reproduce the bug you must follow this steps

 1 language support using any language but English
 2 expire your password with
    $: chage -d 0 $user
   or
    $: passwd -e $user
 3 log out
 4 unity-greeter asks for new password in English
 5 create new password and log in
 6 changes language support for any other language
 7 expire your password again
 8 lock the screen (if you log out lightdm restarts and resets to English)
 9 unity-greeter asks for new password in language chosen in step 1

the wrongly translated sentences are coming from PAM and they are translated with the file

  /usr/share/locale-langpack/pt_BR/LC_MESSAGES/Linux-PAM.mo

for the Portuguese language at least
I thing the error has some to do with wrongly setting the locale in the unity-greeter environment

I'm using ubuntu 16.04, unity-greeter 16.04.2-0ubuntu1