chpasswd fails starting from Alpine 3.6
I’m able to use `chpasswd` to set user password until Alpine 3.5. Starting from Alpine 3.6 I get `PAM: Authentication failure` when I run the command.
To easily reproduce the issue:
$ docker run —rm -it alpine sh
/ # apk add shadow
/ # /usr/sbin/useradd -m -u 1000 new_user
/ # echo “new_user:mypassword” | chpasswd
Password: chpasswd: PAM: Authentication failure
(from redmine: issue id 10209, created on 2019-04-08, closed on 2019-06-19)