Building fedora image failed with "chpasswd: cannot open /etc/passwd"

[Andreas Florath]

When running a fedora-minimal build with devuser element and installing some packages, DIB fails with:

2017-04-09 20:13:13.641277 | [fedora-minimal/build-devuser] dib-run-parts Sun Apr 9 20:13:13 UTC 2017 Running /tmp/in_target.d/install.d/50-devuser
2017-04-09 20:13:13.643224 | [fedora-minimal/build-devuser] + set -eu
2017-04-09 20:13:13.643320 | [fedora-minimal/build-devuser] + set -o pipefail
2017-04-09 20:13:13.643407 | [fedora-minimal/build-devuser] + user_shell_args=
2017-04-09 20:13:13.643517 | [fedora-minimal/build-devuser] + '[' -n /bin/bash ']'
2017-04-09 20:13:13.643612 | [fedora-minimal/build-devuser] + user_shell_args='-s /bin/bash'
2017-04-09 20:13:13.643747 | [fedora-minimal/build-devuser] + useradd -m dib -s /bin/bash
2017-04-09 20:13:13.665029 | [fedora-minimal/build-devuser] + set +x
2017-04-09 20:13:13.665262 | [fedora-minimal/build-devuser] Setting password.
2017-04-09 20:13:13.670883 | [fedora-minimal/build-devuser] chpasswd: cannot open /etc/passwd

Created a CI test case for this:
https://review.openstack.org/#/c/455084/

Link to error message:
http://logs.openstack.org/84/455084/1/check/gate-dib-dsvm-functests-centos-7/e76adb6/console.html#_2017-04-09_20_13_13_641277