postinst and check-support-status.hook: add code to create the d-s-s user's...

postinst and check-support-status.hook: add code to create the d-s-s user's home directory. Closes: #928204.

postinst and check-support-status.hook: add code to create the d-s-s user's
home directory if it doesn't exist, as schroot copies /etc/passwd from the
host without creating the user home directories.
Closes: #928204. Thanks to Santiago Vila.

Signed-off-by: Holger Levsen <holger@layer-acht.org>