The chpasswd command had no custom pam configuration, so the fallback
"other.conf" was used. As this command is non-interactive, this lead to
a "PAM: Authentication failure" error after waiting some seconds.
This fixes bug #10209https://bugs.alpinelinux.org/issues/10209
group = 1000 is not a good default as that can be any group and in
most cases gid=1000 is the chrony group.
adduser in alpine creates usergroups so make use useradd does as well.
